Rapidly solidified submicronic amorphous glass-coated wires have been extensively investigated recently due to their unique combination of reduced diameters (100 to 900 nm), very long sample length (10-2 to 103 m), and bistable magnetic behavior, suitable for both sensing and magnetic logic applications [1].
Here we report on the interaction between domain walls that propagate inside amorphous (Co0.94Fe0.06)72.5Si12.5B15 glass-coated submicronic wires with nearly zero magnetostriction (λ = -1 × 10-7). 
The experimental set-up relies on six pick-up coils (C2 through C7) distributed evenly along the wire and two nucleation coils (C1 and C8) placed at its ends, the entire system being in a long magnetizing solenoid. If there is no signal in the nucleation coils, the sample magnetization reverses from one end (C1) to the other (C8), with only one propagating domain wall being detected successively by the pick-up coils: C2 → C3 → C4 → C5 → C6 → C7.
By applying synchronized rectangular nucleation signals in C1 and C8, magnetization reversal starts at both wire ends. Through the signal amplitudes, we adjusted the time interval between the generation of the two domain walls moving towards each other, and, in this way, the location on the wire axis where the two domain walls would collide. The collision results in a double amplitude peak within one of the pick-up coils, as compared to the peak that corresponds to a single domain wall passing through such a coil. By keeping the nucleation signal constant in C1 at 0.5 mA and varying the signal in C8 between 0.1 and 0.9 mA, one can relocate the domain wall interaction point in any pick-up coil. Fig. 1 shows the displacement of the collision point for an amorphous sample with 750 nm in diameter. 
The results show that the interaction of domain walls in such small diameter cylindrical amorphous wires is fully controllable, which is vital for magnetic logic applications.
Work supported by the Romanian Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI) through project PN-III-P4-ID-PCE-2020-1856 MaDWallS (contract PCE1/2021). 
**References:** [1] S. Corodeanu, C. Hlenschi, C. Rotarescu, H. Chiriac, N. Lupu, T.-A. Óvári, J. Alloy. Compd., Vol. 905, 164260 (2022). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/d355a9fe62bc2e2b132951458fee1cbe.png) 
Fig. 1. Displacement of domain walls interaction point for an amorphous submicronic wire with 750 nm in diameter.

Controlled Domain Wall Interactions in Nearly Zero Magnetostrictive Amorphous Submicronic Wires

The nanocrystalline powders offer opportunities for the design of soft magnetic materials with improved magnetic properties (high saturation magnetization, high permeability, low magnetostriction) to be used for high frequency applications magnetic cores [1-4]. The aim of the work is to develop Fe73.5Cu1Nb3Si13.5B9 powders with a high percentage of particles having the size in the range where nanocrystalline state is directly achieved, by using a new three-jet gas atomization technique (consisting in the use two jets of Ar gas and one jet of water), directed in such a configuration so that the molten alloy jet to be successively fragmented in droplets by the gas jets and further broken intro droplets and cooled by the liquid jet. Powders with the diameter size in the ranges 0-20 µm, 20-32 µm, 32-63 µm, and 63-100 µm have been prepared. Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), thermomagnetic, and magnetic measurements have been performed to assess the structural and magnetic differences of powders between the groups of samples after sieving. The SEM images revealed the formation of particles with almost spherical shape. The X-Ray diffraction patterns show that in the range 0-32 µm the structure of particles is a mixture of amorphous and nanocrystalline phases, approx. 50 % of particles being in amorphous state, which is a quite high percentage. The magnetic measurements, performed using the Vibrating Sample Magnetometer technique (VSM) show that the Curie temperature increases from 350°C to 520°C and the saturation magnetization is between 130 to 145 emu/g. The coercive field, Hc, takes a very low value of 4 Oe for as-cast powders with the smallest diameter range, the value decreasing to down to under 2 Oe after annealing. These properties combined with good thermal stability, low cost price, the possibility to develop components with reduced dimensions/masses, make the amorphous and nanocrystalline alloys competitive and economic solutions in electronics, telecommunications, sensors, etc.
Work supported by the Romanian Ministry of Research, Innovation and Digitalization under NUCLEU Program – contract no. 33N/2019, project PN 19 28 01 01. 
**References:** [1] T. Suzuki, P. Sharma, and L. Jiang, IEEE Trans. Magn., Vol. 54, 2801705 (2018) 
[2] L. Chang, L. Xie, and M. Liu, J. Magn. Magn. Mater., Vol. 452, p. 442 (2018) 
[3] K.L. Alvarez, J.M. Martín, and M. Ipatov, J. Alloys Compd., Vol. 735, p. 2646 (2018) 
[4] K. L. Alvarez, H.A. Baghbaderani, and J.M. Martín, J. Magn. Magn. Mater., Vol. 501, 166457, (2020)

Synthesis of Amorphous and Nanocrystalline Powders by a Three Jet Gas Liquid Technique

The amorphous magnetic wires are widely used as magnetic or magneto-mechanical sensors due to their very soft magnetic properties and high sensitivity to stress. [1-4]. A new design of a high sensitivity sensor with high capability to measure applied forces or load is proposed by this paper. The sensor consists in four pieces of high permeability Co68.18Fe4.32Si12.5B15 amorphous magnetic wire, 120 Î¼m in diameter, 20 mm in length, glued prestressed on a pcb board having 0.3 mm in thickness, 7 mm in width and 30 mm in length (Figure 1). The ends of each wire is soldered on the PCB to form a Wheatstone bridge circuit. The opposite arms of the bridge are placed on the same side of the pcb to increase the bridge unbalance when stressed. Also, all wires forming the bridge arms are parallel and close one to another to minimize the effect of the surrounding magnetic field. By using different PCB support for the bridge, it is possible to tailor the sensitivity and force measuring range. A special designed electronic device was built to power the bridge using a high frequency sinusoidal signal and to extract and amplify the unbalanced voltage of the bridge. The dependence of the output voltage/gain versus applied force, for a signal excitation frequency of 1 MHz, is shown is showin figure 2. The sensor shows linear behavior between Â± 0.15N and sensitivity of 43.7 mV/N, without gain, in the linear region. Financial support by the NUCLEU Program (PN 19 28 01 01) is gratefully acknowledged.

Tailorable force sensor based on stress magneto

The use of magnetic nanoparticles for cancer cell destruction is widely known due to their applications such as magnetic hyperthermia and magneto mechanical actuation
(MMA). Previously, we presented our results regarding a new type of magnetic particles (MPs), i.e. Fe-Cr-Nb-B MPs, prepared by wet milling of superferromagnetic precursor glassy
ribbons, designed for cancer treatment by MMA [1]. These MPs have an important shape anisotropy and a large saturation magnetization, which generates an improved torque in a rotating
magnetic field, producing important damages on the cellular viability of cancer cells. Inspired by these findings, we tested the possibility of using magnetic nanowires (NWs) that have a
higher shape anisotropy. Furthermore, the Fe-Co alloy that we propose has high saturation magnetization values. We prepared Fe64.5Co35.5 NWs with lengths of 4 microns by electrolytic
deposition in alumina membranes with a pore diameter of 200 nm.
The Fe-Cr-Nb-B MPs and Fe-Co nanowires were tested on human osteosarcoma cells (HOS) using various concentrations of particles and found that both are biocompatible in vitro.
Subsequently, we studied the effect of MMA in a rotating 80 Oe magnetic field and frequency of 2 Hz on the viability of HOS. We used MPs and NW with different concentrations, and
exposure time of 30 minutes, applied 24 hours after the introduction of the MPs and NWs into cell culture media. The results indicated that with a concentration of 1 mg/ml of MPs and 0.1
mg/ml of NWs, respectively, the cell viability decreased to about 6-7%. The concentration of NWs needed to induce cancer cell death is 10 times lower than the one needed for MPs. It is
worth mentioning that although NWs are more efficient when using low quantities, due to their higher magnetization and anisotropy, the magnetic nanoparticles are better internalized and
metabolized by cells. Therefore, MPs can be better targeted in tissues harder to reach than NWs. The latter are also harder to control, being more suitable for superficially-developed cancer
tissues.
Supported by (UEFISCDI) Contract no. PCE20/2021 (PN-III-P4-ID-PCE-2020-2381). 

**References:**
 1. H. Chiriac et al. Sci. Rep., 8.11538 (2018)

Cancer cell destruction by magneto mechanical actuation of nanowires compared with nano/micromagnetic particles

Fe-Nb-Cr-B rapidly quenched melt-spun ribbons (MSRs) show glassy structures in the as-quenched state and Curie temperatures (TC) of 290-330 K depending on the Cr content [1]. The medical applications are usually requiring submicron powders, which can be easily targeted to the sick body organs by means of the external magnetic field [2]. The present work focusses on the preparation of Fe67.2Nb0.3Cr12.5B20 submicron powders by high-energy ball milling from MSRs precursors, using different milling agents: oleic acid (OA), sodium oleate (NAOL) and stearic acid (SA). The main challenge is to preserve the glassy structure from MSRs through the milling process, because only the glassy structure guarantees the low TC. MSRs were annealed at 4000C for 1 h to facilitate the milling. The ratio stainless steel balls:powder was of 50:1. The powders milled in OA and NAOL in the ratio of 1:1 have been washed in n-heptane and dried at 700C in vacuum, while for the ones milled in SA, in the ratio of 5:1, trichloroethylene was used for removing the surfactant. After 150 h of milling in OA the powders have ~100 nm, XRD and UHR-TEM investigations indicating the presence of only the glassy structure and the absence of precipitating crystalline phases. The milling up to 250 h reduces the size of the powders to &lt; 50 nm, while the glassy structure is preserved, as confirmed also by the same TC value (~450C) as for the precursor MSRs. The milling in NAOL keeps the powders in the range of 800÷900 nm, while TC remains ~450C. The milling over 100 h in NAOL results in an increase of TC to 650C and of Ms to 45 Am2/kg, compared with MSRs powders milled in OA (Ms = 35 Am2/kg). The increase of TC and Ms is even more obvious for the powders milled in SA (1100C and 112 Am2/kg, respectively). Moreover, the powders milled in SA are not changing their size even after 50 h of milling, i.e. ~5 µm, comparable with the ones of the precursor MSRs. However, the HR-SEM images indicate round shaped powders after milling in SA, compared with the starting lamellar pieces of MSRs, while the XRD and SAED patterns emphasize similar glassy structures for powders and MSRs. Financial support by the NUCLEU Program (PN 19 28 01 01) is gratefully acknowledged.

Influence of wet and dry milling conditions on the evolution of microstructure and TC of Fe-Cr-Nb-B glassy powders

Fluxgate sensors are among the most sensitive devices for the detection of weak magnetic fields (in the range of 10-6 T) with resolutions of 100 pT at room temperature [1]. In conventional configuration, a fluxgate magnetometer consists of two ferromagnetic cores around which two coils for excitation and two coils for detection are wound and differentially connected. The residence times difference (RTD) fluxgate sensor first proposed by Bruno Andò, et al [1] consist of a single soft ferromagnetic core and two coils (one for excitation and one for detection). The sensor detects the external magnetic field strength through its corresponding relationship with the residence times difference of the induced peeks that appear when the excitation field cycles the magnetization of the core. One of the materials showing potential for the development of RTD sensors is represented by the glass-coated microwires exhibiting large Barkhausen effect, i.e., magnetization switching in a single step when the external excitation field is reversed. Recently, a new method to switch the axial magnetization in bistable glass-coated microwires has been reported [2, 3]. The method, detailed in [2], consists in applying a current directly through a magnetic sample subjected to controlled torsion. Using this method as a basis, we report here the development of a new RTD magnetic sensor that does not require an excitation coil. The sensor electronics was built using a dsPIC microcontroller which generates the signal for sensor excitation and measures the time difference between induced peaks (Fig.1). The time resolution of the electronics is about 1/(384x106) s. The sensor performance was studied comparatively using as sensitive elements glass-coated microwires with nominal compositions of the magnetic core Fe77.5Si7.5B15, Co68.18Fe4.32Si12.5B15 and Fe73.5Si13.5B9Cu1Nb3 (FINEMET), having metallic core diameters (Φmetal) of 10, 20 and 30 mm, respectively, and 7 mm glass coating thickness. The transfer functions (time difference versus applied field) were measured for different configuration of the sensor excitation current and torsion values. The value of the sensor sensitivity (S) decreases, and the dynamic range (DR) increases when the excitation current amplitude (I) increases. For annealed Co68.18Fe4.32Si12.5B15 microwires, having a metallic core diameter of 20 μm, we obtained a sensitivity value of 84 μs/(A/m), with a dynamic range of 17 A/m, for an excitation current amplitude of 10 mA. For an excitation current with an amplitude of 40 mA we obtained a sensitivity value of 11.7 μs /(A/m) and a dynamic range of 180 A/m. For current amplitudes of 50 mA and above, the dynamic range decreases due to the fact that the induced peaks become poorly defined, with low amplitudes, and cannot be easily distinguished by the electronic detection system. The annealed Co68.18Fe4.32Si12.5B15 microwires show wider measuring range and higher linearity of the transfer function as compared to all the other analyzed compositions (DR = ± 130 A/m for Φmetal = 20 μm and I=30 mA). The Fe77.5Si7.5B15 microwires show a fairly high noise on the measured transfer graph and lower dynamic range as compared to the Co68.18Fe4.32Si12.5B15 microwires (DR = ± 32 A/m for Φmetal = 20 μm and I=30 mA). The annealed Fe73.5Si13.5B9Cu1Nb3 wires show an extremely low linear variation transfer function (± 9 A/m for Φmetal = 20 μm and I=30 mA) as compared to the other compositions analyzed. For annealed Co68.18Fe4.32Si12.5B15 microwires with different core diameters, we observed that for the same excitation current of 30 mA and the same torsion of 483 Rad/m, the sensitivity of the sensor decreases from 27.7 μs/(A/m) for wires with a diameter of 10 μm, to 12.7 μs/(A/m) for wires having 30 μm in diameter, the dynamic range increasing at the same time from 41 A/m for wires with 10 μm in diameter, to 200 A/m for the samples with 30 μm in diameter (Fig 2). This behavior follows the evolution of the switching field of the same samples, which decreases from 45 A/m for wires with a diameter of 10 μm to 21 A/m for wires with a diameter of 30 μm. The influence of torsion on the transfer function of the sensor is relatively low. Thus, for Co68.18Fe4.32Si12.5B15 wires with a diameter of 30 μm we obtained a sensitivity of 12 μs/(A/m) for a torsion of 120 Rad/m (one end rotation of 450 on a wire with a length of 6.5 mm) and 12.7 μs/(A/m) for 483 Rad/m (one end rotation 1800 on a wire with a length of 6.5 mm). For higher torsion values, a sharp decrease in field sensitivity is observed, most likely due to the strong increase of the mechanical stresses induced in the wire. Work supported by the Nucleu Programme (Project PN 19 28 01 01) and Contract No. 11PFE/16.10.2018 financed by the Romanian Ministry of Education and Research.

**References:**

1. B. Andò, S. Baglio, A.R. Bulsara et al., IEEE Instrum Meas Mag, Vol.8(4), 2005 2. S. Corodeanu, H. Chiriac, A. Damian et al., Scientific Reports, Vol. 9, No. 5868, 2019. 3. V. Zhukova, J. M. Blanco, A. Chizhik et al., AIP Adv. 7, 056026, 2017.

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/bfb14137e3ddfb99b934821adb3b5624.jpg)
Fig. 1. Schematic representation (a) and picture (b) of the RTD fluxgate sensor and the typical output voltage for a sinusoidal excitation signal (c).

![](https://assets.underline.io/uploads/markdown_image/1/image/232054e41dfbb608104ce6b41997f805.jpg)
Fig. 2. The transfer graph obtained for Co68.18Fe4.32Si12.5B15 microwires, annealed at 3000C-1h, having different diameters of the metallic core.

 RTD fluxgate sensors based on current induced magnetization reversal in twisted glass-coated microwires

Due to their special features such as low background noise, high sensitivity, and the possibility of nanoscale fabrication, magnetoresistive (MR) sensors present a great interest for the scientific community, being used especially in biomedical applications [1]. Among MR sensors, those based on tunnel magnetoresistance (TMR) effect exhibit the highest magnetoresistance value, higher sensitivity, and lower power consumption [2, 3]. However, shortcomings as weak linearity in the variation of electric resistance with the applied magnetic field, high coercive field, or quite complicated fabrication process, make the TMR sensors less investigated for biosensing applications. The purpose of this work is to develop a model of TMR based sensor, with small size and high sensitivity, capable of real-time detection of magnetic particles, with possible applications in the detection of magnetic particles from tissues in hyperthermia. The operation of the sensor will be done without magnetic flux concentrators or permanent magnets, therefore no additional steps in the technological process are required. In order to obtain a TMR structure with high values of magnetoresistance and sensitivity, the thicknesses of the component layers were optimized reaching the final configuration: Ta (5 nm)/Ru (20nm)/Ta (5 nm)/CoFe (3 nm)/IrMn (20 nm)/CoFe (2.5 nm)/Ru (0.85 nm)/CoFeB (3 nm)/MgO (1.8 nm)/CoFeB (3 nm)/Ta (10 nm). The thin layers were deposited on Si/SiO2 support (18 x 18 mm2), using the ATC 2200 / AJA International deposition system, which allows both magnetron sputter deposition and electron beam evaporation. Excepting the MgO barrier layer, which was deposited by electron beam evaporation, all other thin layers were obtained by magnetron sputter deposition at a working pressure of 3 mTorr. To induce an in-plane easy axis in the ferromagnetic layers, a magnetic field (100 Oe) parallel to the plane of the thin films, was applied during the deposition. As a detection element, we proposed a structure with a low aspect ratio in the shape of a cylindrical pillar with 4 µm diameter. The total size of each device (sensor and contacts) is 400x250 μm2, as depicted in Fig. 1(a). These small dimensions allow the fabrication of 100 sensors onto single support of 18x18 mm2, leading to a simplification of the technological process. In the first step of the sensor microfabrication, rectangular structures of 40x80 μm2 (Fig. 1(b)) were patterned by e-beam lithography, then ion beam milling and removing of e-resist. The detection element (pillar) and contact surfaces, were defined by electron beam lithography and ion beam milling. In order to passivate the lateral sides of the pillar, 60 nm of insulating layer (SiO2) was sputter-deposited, then the resist and SiO2 from the top of the pillar and contact surfaces were removed by lift-off technique. For measurements, the CPP (“current perpendicular to plane”) configuration was used by passing the electric current perpendicular to the plane of the thin layers. For this step, the electrical contacts with coplanar waveguide geometry (ground-signal-ground), were defined by laser beam lithography followed by Ta (10 nm)/Cu (200 nm) deposition and then lift-off. The coplanar waveguide geometry consists of a middle pad which is the signal strip and two lateral pads that are used as ground lines. The middle pad is connected to the top of the pillar and the two outer pads are connected to the bottom part of the pillar. After microfabrication, TMR sensors were annealed at a temperature of 320 °C in an external magnetic field of 5 kOe, in the direction of anisotropy induced during the deposition. For the as-fabricated TMR sensor, we obtained a magnetoresistance value of 37.5 % and 0.26 %/Oe for the sensitivity. In order to test the TMR sensor, detection experiments were performed using FeCrNbB magnetic particles with a diameter of 50-500 nm obtained by high-energy ball milling from melt-spun ribbons (MSRs) precursors [4]. The magnetic nanoparticles were dispersed in cyanoacrylate adhesives in order to obtain solutions with concentrations of 20 % and 80 %. Then, a glass support was partially covered with these solutions and used to demonstrate the detection capability of the MR sensor. During the measurements, a magnetic field of 20 Oe was applied perpendicular to the direction of the sensor, in order to generate a dipole magnetic field of magnetic particles. The output voltage variation was measured for different concentrations of magnetic particles. As shown in Fig. 2, an output voltage variation of 0.044 mV was obtained for a magnetic particles concentration of 20 %. Increasing the particles concentration to 80%, the variation of the sensor output voltage also increased to 0.161 mV. We demonstrated a dependent relationship between the sensor output voltage and the concentration of magnetic particles. It should also be noted that the values of electrical resistances remain constant over time, indicating the stability of the sensor. Acknowledgment This work was supported by the Romanian Ministry of Research and Innovation (MCI) under the NUCLEU programme, Project PN 19 28 01 01.

**References:**

[1] D. Su, K. Wu, R. Saha et al., Micromachines, Vol. 11, p. 1 (2020) [2] D. D. Djayaprawira, K. Tsunekawa, M. Nagai et al., Applied Physics Letters, Vol. 86, p. 092502-1 (2005) [3] S. Cardoso Freitas, D. C. Leitao, L. Gameiro et al., Microsystem Technologies, Vol. 20, p. 793 (2014) [4] H. Chiriac, N. Lupu, M. Lostun et al., Journal of Applied Physics, Vol. 115, p.17B520-1 (2014)

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/8bc6653b5ea2fe219e2b8925ce30340c.jpg)
Fig. 1. (a) Optical microscope image of a device with G-S-G type electrical contacts and (b) SEM image of a rectangular structure.

![](https://assets.underline.io/uploads/markdown_image/1/image/1b121658e4c6ea5578969a74a9676632.jpg)
Fig. 2. Real-time signal of the TMR sensor for different magnetic particles concentrations.

 Tunnel Magnetoresistance Sensors for Real-Time Detection of Magnetic Nanoparticles

Magnetic particles (MPs) found their usefulness in different cancer treatment applications, such as magnetic hyperthermia, magnetic controlled delivery and release of antitumoral drugs at the targeted site of a tumor, or through magneto-mechanical actuation. Recently, we have introduced a new type of magnetic particles (MPs), prepared by wet milling of superferromagnetic Fe-Cr-Nb-B precursor glassy ribbons, for cancer treatment by magneto-mechanical actuation in low magnetic fields (1÷20 Oe) [1]. The rectangular shapes of newly developed MPs and the superferromagnetism of the glassy alloys of which they are made induce important magnetic shape anisotropies which, in association with a large saturation magnetization, generate an improved torque in a rotating magnetic field, producing important damages on the cellular viability of MG-63 human osteosarcoma (HOS) cells, a form of bone cancer. In this work we studied the possibility of transporting Fe-Cr-Nb-B MPs to areas with cancer cells (HOS), using adipose derived stem cells (ADSC) as carriers, considering their tumor-targeting capacity [2], and the effect of magneto-mechanical actuation of the MPs on HOS viability. Fe-Cr-Nb-B MPs have dimensions between 5 and 100 nm. The Fe-Cr-Nb-B MPs prepared by wet milling were used to obtain a ferrofluid (FF) that was added to the cell culture media before adding it in the cell cultures. Afterwards, HOS and ADSC cells were incubated for 24h with the MPs, and cellular viability assay was performed with MTT (3-(4,5-dimethylthiazolyl-2)-2,5-dyphenytetrazolium bromide). We performed the tests by measuring the cell proliferation rate for 1 mg/ml of particles on both cell types (HOS and ADSC). No cytotoxic effect was observed, the cell proliferation being improved in cell culture incubated with particles. At the same time we performed two tests to confirm the presence of MPs inside both cell types. This was accomplished using transmission electron microscopy (TEM) and colorimetric Ferrozine assay, the latter evaluating the quantity of iron inside the cell. MPs upload by HOS was confirmed using TEM, the particles can be seen both in the extracellular and intracellular medium, being incorporated as single or aggregated particles. Iron quantity per cell was evaluated 48h after adding the MPs to the culture media. We calculated the iron content per cell after subtracting the normal quantity of iron in similar culture condition. ADSC, being larger cells, incorporated larger quantities of MPs (1.12 ng per cell) than HOS (0.31 ng per cell). ADSC cellular migration, both loaded and non-loaded with MPs, was recorded by time-lapse imaging performed using an Evos optical microscope while cells were inside a self-made mini-incubator. Before evaluation, the two cell population (ADSC-MPs and tumor cells) were separated by a free space of about 0.5 mm made mechanically in the co-culture by using a pipette tip (“wound healing” model). The traveled distance of loaded ADSCs towards the zone of the tumor cells was the highest among the evaluated ones. The recorded films showed that MPs-loaded ADSC were able to easily target osteosarcoma cells, moving at twice the speed of the MPs-free ADSC (control sample) in similar cultures (Fig. 1). Magneto-mechanical actuation was performed in a system consisting of four coils placed in cross, which can produce low magnetic field (1÷20 Oe).The destruction of HOS co-incubated with MPs-loaded ADSC was performed through controlled magneto-mechanical actuation (MMA). Magneto-mechanical actuation led to the destruction of ADSC and to the release of MPs on HOS cells, the latter incorporating the released MPs (Fig. 2). By magneto-mechanic actuation, the HOS viability dropped down to 21÷22%. The rotational motion of the irregular shaped MPs produced in the rotating magnetic led to irreversible damages on the cells membranes and organelles, and, subsequently, the cells death. We have successfully showed that Fe-Cr-Nb-B magnetic particles (MPs) are highly biocompatible in vitro. MPs were easily incorporated by ADSC and HOS cells, results confirmed through TEM imaging and Ferrozine assay. MPs loaded ADSCs display increased motility towards tumor cells, compared with their unloaded counterparts. The scope of the study, the destruction of HOS through MMA of the MPs released from ADSC was confirmed through MTT assay. MMA led to the release of the MPs towards tumor cells, the latter being destroyed in high proportion (about 80%) by immediate applying of the MMA. Consequently this method could be successfully implemented in the treatment of bone cancer. Acknowledgements - Work supported by the Romanian Executive Agency for Higher Education, Research, Development and Innovation Funding (UEFISCDI) under contract no. 502PED/2020 (project PN-III-P2-2.1-PED-2019-3442/OPTIMAG).

**References:**

[1] H. Chiriac et al., Scientific Report, Vol. 8, Article Number 11538 (2018). [2] M.G. Scioli et al., International Journal of Molecular Sciences, Vol. 20, p. 3296 (2019).

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/31002254d1c363d3984666805bd7aadc.jpg)
Fig. 1. In vitro cell migration of ADSC loaded and non-loaded, respectively, with MPs towards tumor cells.

![](https://assets.underline.io/uploads/markdown_image/1/image/85d678c0a31d66d5a4895cd0faaa15d6.jpg)
Fig. 2. Cell viability of HOS and ADSC cells, controls and cells with MPs after MM actuation.

 Cancer cells death induced by magneto-mechanical actuation of Fe-Cr-Nb-B magnetic particles carried by Stem cells to the cancer cells area

The high performance permanent magnets are indispensable for many commercial and military applications. Rare-earth hard magnetic nanoparticles have drawn great attention due to their potential applications in nanocomposite permanent magnets with high performance. Different methods have been employed to prepare hard magnetic nanoparticles including chemical methods, electrodeposition, spark erosion and ball milling. The ball milling technique, used for the preparation of nanoparticles, is a simple, inexpensive and efficient method for size reduction of nanocrystalline powders. The experimental parameters involved in ball-milling technique, such as milling time, milling energy, and ball size, are determinant in what concerns the magnetic properties of the nanoparticles. The milling temperature and milling medium are also known as critical factors impacting the morphology and performance of the nanoparticles. Here, we report results on the morphology, structure, and magnetic properties of Ce14Fe76Co4B6 nanoparticles prepared by high-energy ball milling at low temperature, in liquid nitrogen, from nanaocristaline ribbons precursors. At regulate intervals of time, in the milling vial was introduced liquid nitrogen, in order to compensate the evaporation. We found that: (i) the optimal interval for introducing liquid nitrogen into the vial is 20 minutes, since for a longer interval, the liquid nitrogen evaporates and the sample becomes contaminated, (ii) the morphology and size of the powders change with the milling time, from large particles with irregular shapes to small dimensions (about 150 nm) and rounded shapes for a milling time of 420 minutes (the microstructure of powders milled 420 h, is shown in Figure 1.) (iii) the structure and magnetic properties of the nanoparticles were kept close to those of the precursor ribbons by milling in liquid nitrogen (a comparison between the hysteresis curves for powders and the precursor ribbons is shown in Figure 2). The Ce14Fe76Co4B6 nanoparticles obtained by ball milling in liquid nitrogen have great potential to be used for the production high performance nanocomposite permanent magnets. Acknowledgement This work was supported by a grant of the Romanian Ministry of Education and Research, CCCDI - UEFISCDI, project number PN-III-P2-2.1-PED-2019-2054, within PNCDI III. &lt;!--![endif]----&gt;&lt;!--![endif]----&gt;&lt;!--![endif]----&gt;

**References:**

[1] Baolu Zhou, Zhongxue Li and Congcong Chen, Global Potential of Rare Earth Resources and Rare Earth Demand from Clean Technologies, Minerals 7 (2017) 203. [2] Thanh Anh Huynh and Min-Fu Hsieh, Performance Analysis of Permanent Magnet Motors for Electric Vehicles (EV) Traction Considering Driving Cycles, Energies 11 (2018) 1385. [3] M. Grigoras, M. Lostun, G. Stoian, D.D. Herea, H. Chiriac, N. Lupu, Microstructure and magnetic properties of Ce10+xFe84−xB6 nanocrystalline ribbons versus preparation conditions, J. Magn. Magn. Mater. 432 (2017) 119–123. [4] J. F. Herbst, M. S. Meyer and F. E. Pinkerton, Magnetic hardening of Ce2Fe14B, J. Appl. Phys. 111, 07A718 (2012).

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/eaaa31845ba980e59e6fd93570814151.jpg)
Fig 1. The SEM micrograph of Ce14Fe76Co4B6 
powders milled 420 h in liquid nitrogen.

![](https://assets.underline.io/uploads/markdown_image/1/image/c84ddc682ad13f3ca51fdaac70d5be13.jpg)
Fig 2. The hysteresis curve of Ce14Fe76Co4B6 ribbons (black) and powders (red) milled 420 h in liquid nitrogen.

 Characterization and Magnetic properties of Ce-FeCo-B Nanoparticles Prepared by Cryo-milling

Submicron and nanosized cylindrical amorphous Fe77.5Si7.5B15 and (Co0.94Fe0.06)72.5Si12.5B15 wires with diameters between 100 and 900 nm have been successfully cast by means of an upgraded variant of the glass-coated melt spinning technique [1]. Amorphous samples with both compositions show a magnetically bistable behavior, i.e., a single step axial magnetization reversal with a characteristic rectangular hysteresis loop. This reversal consists in the displacement of a 180-degree domain wall along the wire axis when the applied field is equal to or larger than the switching field. The values of the switching field are significantly different, with the positive magnetostrictive amorphous submicron wires (Fe77.5Si7.5B15) displaying one to two orders of magnitude larger values than the nearly zero magnetostrictive (Co0.94Fe0.06)72.5Si12.5B15 ones. This emphasizes the importance of the types and magnitudes of the intrinsic magnetic anisotropies. Here we report on the study of structural relaxation within the amorphous submicron wires using measurements of the 180-degree domain wall velocity, in order to gain deeper insights into the roles played by the various types of magnetic anisotropy in amorphous submicron wires with different magnetostriction, such as Fe77.5Si7.5B15 with the magnetostriction constant of 25 × 10-6 and (Co0.94Fe0.06)72.5Si12.5B15 with the magnetostriction constant of -1 × 10-7, respectively. The samples have been furnace annealed in vacuum at 200°C and 350°C for 1h, in order to induce structural relaxation phenomena in the amorphous phase without crystallization. Domain wall velocity measurements have been performed on as-cast and annealed samples with both compositions and different diameters, using a method developed specifically for such ultrathin cylindrical wires [2]. Fig. 1 shows the dependence of the domain wall velocity on the annealing temperature for highly magnetostrictive amorphous Fe77.5Si7.5B15 samples with diameters between 230 and 850 nm. Fig. 2 illustrates the same dependence in the case of nearly zero magnetostrictive (Co0.94Fe0.06)72.5Si12.5B15 samples with 300 and 770 nm in diameter, respectively. The domain wall velocity increases monotonically with the annealing temperature for all the highly magnetostrictive samples. The slope of the curves decreases with the increase in the wire diameter. This behavior originates in the stress relief that accompanies the structural relaxation and shows the important role played by the magnetoelastic anisotropy in the Fe77.5Si7.5B15 samples. The effect is more pronounced in the thinner samples, due to their stronger intrinsic magnetoelastic interaction. A completely different behavior has been observed in the nearly zero (Co0.94Fe0.06)72.5Si12.5B15 samples. For a wire with 770 nm in diameter, a monotonic decrease of the domain wall velocity with the annealing temperature was observed. For a thinner one, with 300 nm in diameter, a change of slope was observed: the wall velocity slightly increases after annealing at 200°C, and then drops below the value of as-cast sample after annealing at 350°C. This behavior is consistent with a diminished role of the magnetoelastic anisotropy and a more prevalent role of the shape anisotropy. Only the latter is important in the thicker sample. In the thinner one, the magnetoelastic anisotropy contributes to the magnetic behavior until a sufficiently large annealing temperature is used, so that the residual stresses are decreased. The results show that measuring the domain wall velocity of amorphous submicron wires with different magnetostriction constants can provide essential information on the structural relaxation effects by means of the dominant magnetic anisotropy type and its changes triggered by the low temperature annealing process. This analysis is important for the future application of cylindrical amorphous submicron wires. Acknowledgements - Work supported by the Romanian Executive Agency for Higher Education, Research, Development and Innovation Funding (UEFISCDI) under contract no. 511PED/2020 (project PN-III-P2-2.1-PED-2019-0586/NanoCyliCon).

**References:**

[1] T.-A. Óvári, N. Lupu, and H. Chiriac, Recent trends in magnetic nanowires and submicron wires prepared by the quenching and drawing technique, in Magnetic Nano- and Microwires (Second Edition), edited by M. Vázquez (Woodhead Publishing, Cambridge, 2020), pp. 221-253. [2] S. Corodeanu, H. Chiriac, and T.-A. Óvári, Accurate measurement of domain wall velocity in amorphous microwires, submicron wires and nanowires, Rev. Sci. Instrum. 82 (2011) 094701.

**Images:**

![](https://assets.underline.io/uploads/markdown_image/1/image/d460a15c063e392de7c341532897f628.jpg)
Fig. 1. Domain wall velocity vs. annealing temperature for highly magnetostrictive amorphous Fe77.5Si7.5B15 glass-coated submicron wires.

![](https://assets.underline.io/uploads/markdown_image/1/image/2b1a79db360ef8ca5113605e7160f667.jpg)
Fig. 2. Domain wall velocity vs. annealing temperature for nearly zero magnetostrictive amorphous (Co0.94Fe0.06)72.5Si12.5B15 glass-coated submicron wires.

 Correlation between Structural Relaxation and Magnetic Behavior in Amorphous Submicron Magnetic Wires

The magnetization switching in glass-coated amorphous nanowires with cylindrical symmetry is presented and discussed. We studied the coercive field dependence of the nanowires dimensions in order to understand the main aspects of the magnetization reversal processes in amorphous nanowires with cylindrical symmetry. The considered samples were two alloys with representative compositions: (1) the alloy (Co0,94Fe0,06)72,5Si12,5B15, with very small negative magnetostriction, considered, from this reason, almost zero; and (2) the alloy Fe77,5Si7,5B15, with a positive magnetostriction. In order to substantiate the approach taken, we simulated the axial hysteresis loops for amorphous nanowires with various diameters, whilst keeping a constant sample length. The results, illustrated in Figure 1, reveal the fact that the coercive field decreases when the diameter is larger. This dependence is related to the value of the shape anisotropy, which increases with the ratio between length and diameter. The simulated loops allowed us to understand the effect of anisotropy on coercivity. For the magnetoelastic contribution, we used a simple anisotropy distribution to calculate the axial hysteresis loops in the case of glass-coated Fe77.5Si7.5B15 amorphous nanowires. The results, for different magnitudes of the magnetoelastic anisotropy, are shown in Fig.2. One observes that the magnetoelastic contribution clearly affects the remanence of the axial hysteresis loops. A smaller squareness also shows an easier nucleation of a domain with reversed magnetization. The use of such cylindrical nanowires in magnetic logic gates is straightforward, given their bistable behavior which paves the way for application in new miniaturized devices [1]. Acknowledgement: Work supported by the Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI) under the project PN-III-P4-ID-PCE-2020-1856 (contract no. PCE 1/2021).

![](https://assets.underline.io/uploads/markdown_image/1/image/197b3e03e30de3198a8693848bcd624e.jpg)

Fig. 1 Hysteresis loops of cylindrical amorphous nanowires with different diameters and compositions.

![](https://assets.underline.io/uploads/markdown_image/1/image/4884a95693a04dfe9ca0274e826a4e4a.jpg)

Fig. 2 Hysteresis loops for different anisotropy distributions: (i) monotonous distribution (MD) with various amplitudes; and (ii) nonlinear distribution (NLD).

Micromagnetic study of anisotropy in cylindrical amorphous nanowires

Rapidly solidified amorphous wires with diameters below 1 μm have opened up new miniaturization opportunities for sensing devices and created new application possibilities [1]. Here we report on an in-depth study of magnetization switching in nearly zero magnetostrictive (Co0.94Fe0.06)72.5Si12.5B15 amorphous wires with diameters between 300 and 450 nm, prepared by an improved variant of glass-coated melt spinning. Hysteresis loops were measured using a method developed specifically for thin wires [2]. All samples were magnetically bistable, exhibiting a rectangular axial loop. Hence, magnetization reversal takes place by depinning and subsequent propagation of a single domain wall when the applied field H reaches the value of the switching field, H*. We measured the domain wall velocity at various values of H, starting from H = H* up to the maximum employed value, Hmax = 10 000 A/m. The most remarkable results are shown in Fig. 1, which illustrates both the switching field and the domain wall velocity vs. sample diameter. Both exhibit strongly nonlinear variations with the diameter. Also, the slopes of the curves are always opposite to one another. The nonlinear shape of wall velocity vs. sample diameter is maintained even at larger fields, up to H = Hmax. The maximum wall velocity at H = H*, i.e. 1450 m/s, was observed for a sample with 410 nm in diameter. Domain wall velocity increases monotonically with applied field for all samples. Fig. 2 shows the field dependence of domain wall velocity for the 410 nm sample, with a maximum of nearly 4000 m/s at H = Hmax. The nonlinear effects have been attributed to the nonlinear distribution of intrinsic frozen-in stresses, that are inherent to the rapid solidification preparation process. The results allow one to accurately control and tailor the magnetic behavior of these ultrathin magnetic wires for specific applications. Work supported by the Romanian Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI) through project PN-III-P4-ID-PCE-2020-1856 MaDWallS (contract no. PCE1/01.02.2021).

![](https://assets.underline.io/uploads/markdown_image/1/image/a970aba3063dffb28164de150a42efa1.jpg)

Fig. 1. Switching field & wall velocity vs. sample diameter.

![](https://assets.underline.io/uploads/markdown_image/1/image/00e3b06de01dbc5ecfa81be5b8357d0f.jpg)

Fig. 2. Domain wall velocity vs. applied field for a 410 nm in diameter sample.

Nonlinear Effects in the Magnetization Switching of Nearly Zero Magnetostrictive Amorphous Submicron Wires

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**Session Chair:** Cristina Bran, *Instituto de Ciencia de Materiales de Madrid*

JPA: Amorphous and Nanocrystalline Soft Magnets II

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COA - Soft Magnetic Materials I: Amorphous and Nanocrystalline

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IS: Magnetic Field Sensors II

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Nicoleta Lupu

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