United States

In recent years there is a growing interest in synthesizes of novel iron-based nanoparticles and nanocomposites with high efficiency of thermal energy transfer suitable for use in magnetic fluid hyperthermia. The development of novel biocompatible magnetic nanoparticles (MNPs) for biomedical applications has been the subject of extensive exploration over the past two decades. Here we study the characteristics of carbon-coated ferromagnetic (Fe-Fe3O4)@C “core-shell” nanoparticles in samples with different concentration of iron synthesized by a solid-phase pyrolysis (SPP) of iron phthalocyanine (FeC32H16N8) molecules. The sample with higher iron concentration additionally annealed at 250°C under the oxygen media produces (Fe3O4) shell on Fe nanoparticles. The structural and magnetic properties of these nanomaterials were conducted using Scanning Electron Microscope (SEM), High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images with elemental mapping data, Raman spectroscopy, X-ray diffraction (XRD), magnetometry, electron paramagnetic and ferromagnetic resonances (EPR, FMR). The STEM image in Fig. 1 demonstrates a presence of Fe-Fe3O4 “core-shell” nanoparticles of order ~ 50 nm with oxide shells in carbon matrix. The ferromagnetic hysteresis loops with residual magnetizations and coercive forces is shown in Fig. 2 at two different temperatures. The characteristics of magnetic heating of water-based solution with different concentrations of synthesized nanocomposites under the influence of an external magnetic field have been studied. The magnetic characteristics such as saturation magnetization and coercivity as well as the specific absorption rate (SAR) make these materials attractive for magnetic hyperthermia applications.This work was supported by European Union’s Horizon 2020 research and innovation programme under grant agreement No 857502 (MaNaCa). The work at CSULA supported by the NSF CREST Grant #HRD-1547723.&lt;br&gt;

**References**

Fig. 1 High-resolution transmission electron microscopy images of iron/iron-oxide nanoparticles with core-shell architecture embedded in carbon matrix&lt;br&gt;


Fig. 2 Magnetization versus magnetic field shown for Fe-Fe3O4 nanoparticles at 3K and 300K



MMM 2022

Syntheses and Characterization of Core Shell Iron

In recent years there is a growing interest in synthesizes of novel iron-based nanoparticles and nanocomposites with high efficiency of thermal energy transfer suitable for use in magnetic fluid hyperthermia. The development of novel biocompatible magnetic nanoparticles (MNPs) for biomedical applications has been the subject of extensive exploration over the past two decades. Here we study the characteristics of carbon-coated ferromagnetic (Fe-Fe3O4)@C “core-shell” nanoparticles in samples with different concentration of iron synthesized by a solid-phase pyrolysis (SPP) of iron phthalocyanine (FeC32H16N8) molecules. The sample with higher iron concentration additionally annealed at 250°C under the oxygen media produces (Fe3O4) shell on Fe nanoparticles. The structural and magnetic properties of these nanomaterials were conducted using Scanning Electron Microscope (SEM), High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images with elemental mapping data, Raman spectroscopy, X-ray diffraction (XRD), magnetometry, electron paramagnetic and ferromagnetic resonances (EPR, FMR). The STEM image in Fig. 1 demonstrates a presence of Fe-Fe3O4 “core-shell” nanoparticles of order ~ 50 nm with oxide shells in carbon matrix. The ferromagnetic hysteresis loops with residual magnetizations and coercive forces is shown in Fig. 2 at two different temperatures. The characteristics of magnetic heating of water-based solution with different concentrations of synthesized nanocomposites under the influence of an external magnetic field have been studied. The magnetic characteristics such as saturation magnetization and coercivity as well as the specific absorption rate (SAR) make these materials attractive for magnetic hyperthermia applications.This work was supported by European Union’s Horizon 2020 research and innovation programme under grant agreement No 857502 (MaNaCa). The work at CSULA supported by the NSF CREST Grant #HRD-1547723. 

**References**

Fig. 1 High-resolution transmission electron microscopy images of iron/iron-oxide nanoparticles with core-shell architecture embedded in carbon matrix 


Fig. 2 Magnetization versus magnetic field shown for Fe-Fe3O4 nanoparticles at 3K and 300K

poster

#### Welcome to the 67th Annual Conference on Magnetism and Magnetic Materials, MMM 2022!

The Conference was held from October 31 to November 4 and offers both in-person and on-demand content.

MMM 2022 is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a tutorial, and several special sessions. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

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This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

The unidirectional spin Hall magnetoresistance (USMR) is initially discovered in ferromagnetic (FM) and normal metal (NM) structures[1] and magnetic semiconductor structures[2]. It is a phenomenon observed in bilayer structures and is related to interfacial spin generation and scattering processes at the interface. The similar unidirectional spin Hall and Rashba-Edelstein magnetoresistance (USRMR) is observed in FM-topological insulator (TI) bilayers being much larger than that in FM-NM bilayers in bilayer structures[3]. They are of particular interest due to its potential of 180-degree sensitive electrical readout of magnetization in bilayer structures for spin-orbit torque switching devices.
Here, we report large unidirectional spin Hall and Rashba−Edelstein magnetoresistance in a new material family - magnetic insulator (MI)/TI Y3Fe5O12 (YIG)/Bi2Se3 bilayers. Such heterostructures exhibit a USRMR that is about an order of magnitude larger than the highest values reported in all-metal Ta/Co bilayers[1]. The polarized neutron reflectometry (PNR) reveals a unique temperature-dependent magnetic intermediary layer at the MI-substrate interface and a proximity layer at the MI-TI interface. These PNR findings echo the magnetoresistance results in a comprehensive physics picture. Finally, we demonstrate a prototype memory device based on a MI/TI bilayer, using USRMR for electrical read out of current-induced magnetization switching aided by a small Oersted field[4].
 
**References** [1] C. O. Avci, K. Garello, A. Ghosh et al., Nat. Phys., vol. 11, no. 7, p. 570–575 (2015)
[2] K. Olejník, V. Novák, J. Wunderlich et al., Phys. Rev. B - Condens. Matter Mater. Phys., vol. 91, no. 18, p. 180402 (2015)
[3] Y. Lv et al., Nat. Commun., vol. 9, no. 1, p. 111 (2018)
[4] Y. Lv et al., Appl. Phys. Rev., vol. 9, no. 1, p. 011406, (2022) 
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Large unidirectional spin Hall and Rashba−Edelstein magnetoresistance in topological insulator/magnetic insulator heterostructures

Recent studies revealed that spin diffusion length (λs) and spin lifetime (τs) of electrons in Ge are governed by spin-flip scattering among conduction band valleys (intervalley spin-flip scattering) [1]. To reduce the intervalley spin-flip scattering frequency, Tang et al. have theoretically predicted that lifting the degenerate four valleys through a lattice strain is effective [2]. In this study, we experimentally study the effect of strain on spin transport in strained Si0.1Ge0.9, which exhibits a Ge-like electronic band structure.
A strained n-Si0.1Ge0.9 spin transport layer (~70 nm) with a carrier concentration (n) of ~1×1018 cm-3 was grown on Ge/Si(111) substrates by molecular beam epitaxy (MBE), where the in-plane tensile strain of ~0.66% was confirmed by reciprocal space map. Then, we fabricated lateral spin-valve (LSV) devices with a Co-based Heusler alloy spin injector/detector [3,4]. A representative four-terminal nonlocal spin signal (|ΔRNL|) at room temperature is shown in the inset of Fig. 1. Figure 1 shows contact distance (d)-dependent |ΔRNL| at room temperature for LSV devices with the strained n-Si0.1Ge0.9 and an n-Ge. The dashed lines are fits to the data using |ΔRNL| ∝ exp(-d/λs) and the estimated value of λs for the strained n-Si0.1Ge0.9 (n-Ge) is estimated to be ~0.93 µm (~0.50 µm). Notably, an approximately twofold increase in λs is attributed to the enhanced electron mobility and spin lifetime, induced by lifting the valley degeneracy and by obtaining relatively low carrier concentration [5]. We also demonstrate long-distance spin-drift transport under the electric field (E) and clearly observe pronounced Hanle oscillations with d = 7 µm at T = 50 K in a three-terminal measurement with a drift current of ID = -0.5 mA, as shown in Fig. 2. 
**References** [1] K. Hamaya et al., J. Phys. D: Appl. Phys., Vol. 51, p.393001 (2018)
[2] J. -M. Tang et al., Phys. Rev. B, Vol. 85, p.045202 (2012)
[3] M. Yamada et al., NPG Asia Mater., Vol. 12, p.47 (2020)
[4] K. Kudo et al., Appl. Phys. Lett., Vol. 118, p.162404 (2021)
[5] T. Naito et al., Phys. Rev. Applied (accepted)
 
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Long distance spin transport in strained SiGe

Magnetic nanoparticles (NPs) provide an ideal support for developing a wide range of nanotechnologies and biomedical applications, such as drug-delivery, gene delivery,
hyperthermia, or contrast agents for MRI.[1] Magnetite (Fe3O4
) NPs are good candidates for these applications due to their non-toxicity and long-life in the bloodstream. To optimize these
applications, it is crucial to well control the magnetic response of individual NP when manipulating a collection of them via a magnetic field. In particular, it is useful to identify any
interparticle magnetic correlations that may cause the magnetic response to deviate from superparamagnetism, induce superferromagnetism and magnetic hysteresis, and affect the
dynamics of fluctuations. To that end, we have studied the magnetic response of 5 – 100 nm Fe3O4 NPs and its dependence on NP size, using magnetometry [2] and spin muon resonance
[3]. However, this information remains macroscopic or spatially averaged. Here we show how nanoscale spatial information on inter-particle magnetic correlations can be obtained via xray resonant magnetic scattering (XRMS) [4] as illustrated in Figure 1. By tuning the energy of the x-rays to resonant edges of Fe and comparing opposite polarization helicities, we have
extracted information about the local inter-particle magnetic orders within NP assemblies of various sizes.[5] We fitted the XRMS data using a model based on chains of NPs.[6] The data
fitting shows ferromagnetic ordering when an external magnetic field is applied, and the emergence of antiferromagnetic ordering, competing with magnetic randomness, when the field is
brought back near the coercive point (zero net magnetization). We studied how these correlations depend on particle size and found an enhancement of magnetic couplings and
antiferromagnetic orders for bigger particles. [7] Additionally we will show preliminary studies of the dynamics of magnetic fluctuations via x-ray photon correlation spectroscopy (XPCS). 
**References** 
1. Frey et al., Chem. Soc. Rev. 2009, 38, 2532-2542 (2009) 
2. Klomp et al., IEEE Trans. Mag. 56, 2300109 (2020) 
3. Frandsen et al., Phys. Rev. Matter 5, 054411 (2021) 
4. Kortright et al., Phys. Rev. B 71, 012402 (2005) 
5. Chesnel et al., Magnetochemistry 4, 42-58 (2018) 
6. Rackham et al., AIP Advances 9, 035033 (2019) 
7. Rackham et al., to be submitted (2022) 

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Figure 1: Layout of the x-ray resonant magnetic scattering (XRMS) measurement of a nanoparticle assembly.

Interparticle magnetic correlations and dynamics of fluctuations in assemblies of Fe3O4 nanoparticles

Magnetic skyrmions are vortex-like spin textures. They are topologically protected from external perturbation and can be driven with extremely low currents. Therefore, they have been paid much attention and they are expected to be applied to the spintronic devices such as the magnetic memories and the logic devices. They can be discovered in so-called chiral magnets which are lacking in the inversion symmetry. The one of the characteristics of the chiral magnets is non-vanishing Dzyaloshinskii-Moriya interaction (DMI). The DMI, which tilts the neighboring spins, is an essential interaction to stabilize the magnetic skyrmions. The characteristics of the DMI are determined by the symmetry of the system. The Neel-type skyrmions are generally observed in Cnv symmetric thin film materials. Recently, the elliptical skyrmions have been observed and they are stabilized in the C2v symmetric systems. This is because the different values of the DMI constants of the x-axis and y-axis can be allowed in the C2v symmetric systems. The elliptical skyrmions have several advantages in comparison with circular skyrmions when applied to the spintronic devices. For example, the skyrmion Hall angles of the elliptical skyrmions can be controlled by changing the shapes of them [1]. In this study, we investigate both the dynamics and the phase diagram of elliptical ferromagnetic skyrmions. We consider Co thin films on W as ferromagnetic materials [2]. We drive the elliptical skyrmions by applying the spin current in the x-direction. Figures 1 and 2 show the dependences of the velocity (|v|) and the skyrmion Hall angle (θSkHE) on the elliptical ration (b/a), respectively. Here, a (b) is the length of major (minor) axis of the elliptical skyrmions. We find that |v| increases with the decreasing the value of b/a and θSkHE decreases with the decreasing the value of b/a Therefore, the elongated skyrmions along the current direction are useful in comparison with the circular skyrmions when applied to the spintronic devices. At the conference, we are going to show the phase diagrams and discuss the regions where the elliptical skyrmions appear. 
**References** 
J. Xia, X. Zhang, M. Ezawa, Q. Shao, X. Liu, and Y. Zhou, Appl. Phys. Lett., Vol. 116, p.022407 (2020) 
L. Camosi, J. PeñaGarcia, and J. Vogel et al, New J. Phys., Vol. 23, p.013020 (2021) 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/8e967bd96ed03513ee0b331aacc4912e.png) 
Fig. 1 The dependence of |v| on b/a. 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/edf45e69357d05e62f0bbe4ab1c3ca6b.png) 
Fig. 2 The dependence of θSkHE on b/a.

Elliptical Ferromagnetic Skyrmions

In magnonic and spintronic devices, a low magnitude magnetic damping is desired for efficient operation via the long-range propagation of spin waves [1]. However, thin magnetic ferrite films (low damping but insulating) may not suffice if a charge current is needed [2]. Thin films of the conducting binary alloy of cobalt and iron (Co25Fe75) have exhibited low damping (~10-3) [3]. To further decrease the damping of this system, a multilayer film consisting of ten 10 nm layers of Co25Fe75 alternated with 2 nm layers of hafnium (Hf) is proposed. This structure would decrease the damping by preventing eddy current losses and decrease coercivity and magnetic saturation via smaller crystallite sizes [4,5]. These single and multilayer films were deposited via sputtering, with thicknesses (t) of 10, 50, and 100 nm. The ferromagnetic resonance (FMR) of the films showed as the t increases, at a constant frequency (17 GHz shown), the FMR field decreases and linewidth increases, but the 100 nm multilayered film maintains the linewidth and FMR field of the 10 nm film (Fig. 1). The linewidth and FMR for each film (at 14-17 GHz) in addition to the saturation magnetization were used to calculate the damping parameter (α) of each film. This showed that as t increases up to 100 nm, the damping increases from ~1x10-2 (10 and 50 nm) to ~8x10-2 (100 nm) (Fig. 2). The damping of the multilayered film (~5x10-3) is below that of the 10 nm film, an order of magnitude improvement. This work shows that increasing t for single layered Co25Fe75 decreases FMR field, increases linewidth, and increases damping. The multilayer structure shows the ability to tune the FMR and damping. This provides avenues for other heterostructures, including the use of an insulating interlayer or other magnetic materials. 
**References:** [1] H. Glowinski, F. Lisiecki, P. Kuswik, J. Alloys Compd., 785, 891-896 (2019). 
[2] E. Edwards, H. Nembach, and J. Shaw, Phys. Rev. Appl., 11, 054036 (2019). 
[3] R. Weber, D. Han, I. Boventer, J. Phys. D: Appl. Phys., 52, 325001 (2019) 
[4] S. Balaji and M. Kostylev, J. Appl. Phys., 121, 123906 (2017). 
[5] L. Garten, M. Staruch, K. Bussmann, ACS Appl. Mater. Interfaces, 14, 25701-25709 (2022). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/bf9f3851b4e267d6a47336d9f874f7b2.png) 
Fig. 1. FMR measurements of the CoFe films at 17 GHz, showing a decrease in FMR field and increase in linewidth as thickness increases, and the multilayer sample returns to the FMR and linewidth of the 10 nm film. 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/275607c48d5ec3ed3b02592fd99e8110.png) 
Fig. 2. Calculated damping parameters of the CoFe films, showing that the multilayered film damping (0.0055) is comparable to a typical low damping value of CoFe (0.005) [3].

Fabrication of Co25Fe75/Hf multilayer thin films to decrease the magnetic damping coefficient

Heat capacity is a basic physical quantity most important for studying magnetocaloric materials. Not only it reflects how much heat can be stored in the material, but it also allows to quantify the two main performance parameters: the isothermal entropy change Î”S and the adiabatic temperature change Î”Tad. On top of that, being sensitive to structural, electronic and magnetic degrees of freedom, heat capacity also provides fundamental insights. In Fe2P materials, at the exception of the binary parent, heat capacity studies were so far limited to indirect determinations of the magnetocaloric effect. Here, we will present an extensive heat capacity study of a prototypical MnFe(P,Si,B) compound. Semi-adiabatic relaxation calorimetry, commercial heat flow and home-made Peltier cells differential scanning calorimeters were used to record the heat capacity both around first-order ferromagnetic transition and at low temperatures. This systematic investigation fills several knowledge gaps on the promising MnFe(P,Si,B) magnetocaloric materials. First, we will describe the development of a Peltier cell differential scanning calorimeter designed â€œas an optionâ€ for commonplace commercial cryostat equipped with high magnetic field. This system can be used to measure directly the isothermal entropy change Î”S induced by a magnetic field and it even allows targeting the cyclic (reversible) effect due to successive magnetization/demagnetization. In MnFe0.95P0.585Si0.34B0.075, an exceptionally large cyclic entropy change at intermediate field (Î”Scyclic = 13.2 J kg-1 K-1 for Âµ0Î”H = 1 T) is observed. Then, the heat capacity is analyzed over a broad temperature range to provide an estimate of several important parameters, such as the electronic density of states (N(EF)â‰ˆ 7.2 states eV-1f.u.-1) or an estimate of the Debye temperature Î¸D â‰ˆ 455 K. Different methods (non-magnetic reference, Debye function, phonons calculations) were used to model the lattice contribution to the heat capacity. Our study highlights the difficulty to disentangle lattice, electronic and magnetic contributions in Fe2P-type materials. It nonetheless reveals that the magnetic entropy plus latent heat is considerably larger in MnFe(P,Si,B) than in the parent Fe2P.

Heat Capacity and Giant Magnetocaloric Effect of a MnFe(P,Si,B) Compound investigated by semi adiabatic and Peltier Cell Calorimetry Techniques

Magnetic force microscope (MFM) is a type of scanning probe microscope (SPM) that detects and images the gradient of the stray magnetic field of the observed sample. Therefore, the magnetic domain image is greatly affected by the surface morphology of the probe and the magnetic properties of the coated magnetic thin film. If the strong stray magnetic field for the permanent magnet material disturbs the magnetization of the magnetic probe, accurate observation of the magnetic domain structure is difficult. L10 ordered FePt alloy with high uniaxial magnetocrystalline anisotropyis thought to be an candidate probe material because of its high corrosion resistance and high coercivity[1]. It has also reported that the orientation of the FePt layer can be controlled by introducing MgO layer[2]. However, there are only a few reports of magnetic domain images observed by MFM probes using FePt film. In this study, the orientation of the FePt layer was controlled by using a MgO under layer with varying film thickness and element additions in order to observe high-resolution magnetic domain images. The FePt coated probes were prepared using an ultra-high vacuum magnetron sputtering system. A MgO buffer layer was deposited on Si cantilever and Si substrate at room temperature (R.T.). Then, FePt was deposited at a substrate temperature Ts of 873 K and they were annealed at 973 K. The surface morphology of the probes was observed by scanning electron microscope (SEM). The crystal structure was evaluated by X-ray diffraction (XRD), and the magnetic properties weremeasured usinga superconducting quantum interference device (SQUID) magnetometer. From XRD patterns, the fundamental (002) and the superlattice (001) peaks from L10 ordered FePt phase have been clearly observed atthe FePt probe by the introduction of MgO buffer layer, and a clear magnetic domain image was observed. However, when a Cu-doped MgO layer was used, the peak intensity from the L10ordered FePt phase increased and a magnetic domain image with even higher resolution was obtained. High-resolution mechanism will be discussed at the conference.

Preparation of probes for high resolution magnetic force microscopy by orientation control of FePt layer

Transcranial magnetic stimulation (TMS) [1] is a non-invasive pain-free medical technology clinically approved for treatment of drug-resistant depression [2, 3]. TMS uses
pulsed magnetic fields to induce eddy currents [4] in the brain. The biological mechanism of rTMS effects is tought to be mostly relying on the long-lasting changes of the neuronal
excitability and the brain functional plasticity, respoectively [5]. However, the effects of TMS-like fields on non-neuronal cells and artificial systems are almost unknown. The aim of this
study was to explore the potential of repetitive magnetic stimulation (RMS) performed by TMS devices in oncology, controllable drug release and regenerative medicine applications.
Using a standard TMS device “Magstim Rapid2”, we examined effects of >30 experimental regimes of RMS on viability and phenotype of various tumour (glioblastoma, pancreatic, liver,
colorectal [6] and breast cancers) and immune cells (microglia and macrophages). We also tested the effect of RMS on drug release from polymer nanoparticles and reactive oxygen species
generation (ROSG) in cancer and immune cells. Finally, we examined the combined effects of RMS and drugs targeting tissue growth.
RMS selectively modulated viability and functional polarisation of microglia and macrophages in a frequency/intensity-dependent manner and affected the proliferation/viability of cancer
cells (cancer type, frequency- and pulse number-dependent up- and downregulation). RMS induced triggering of drug release from nanoparticles, enhancement of ROSG and additive drug
effects.
Our pioneering findings demonstrate the potential of TMS technology repurposing for immunomodulation, cancer treatment, and drugs and nanomedicines treatment.
We thank Sydney Vital (for seed grant) and Medilink Australia (for providing the “Magstim”). The authors gratefully acknowledge the support of the Macquarie University FMHHS
Laboratory Operations Team. A.G. is thankful for support of her work by the Macquarie University Research Fellowship. 

**References:** 

1. A. T. Barker, R. Jalinous, and I. L. Freeston, "Non-invasive magnetic stimulation of human motor cortex," Lancet, vol. 1, no. 8437, pp. 1106-7, May 11 1985, doi:
10.1016/s0140-6736(85)92413-4. 
2. A. T. Barker, I. L. Freeston, R. Jalinous, and J. A. Jarratt, "Magnetic stimulation of the human brain and peripheral nervous system: an introduction and the results of an initial clinical
evaluation," Neurosurgery, vol. 20, no. 1, pp. 100-9, Jan 1987, doi: 10.1097/00006123-198701000-00024. 
3. P. M. Rossini et al., "Non-invasive electrical and magnetic stimulation of the brain, spinal cord, roots and peripheral nerves: Basic principles and procedures for routine clinical and
research application. An updated report from an I.F.C.N. Committee," Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology, vol. 126, no.
6, pp. 1071-1107, Jun 2015, doi: 10.1016/j.clinph.2015.02.001. 
4. M. Hallett, "Transcranial magnetic stimulation and the human brain," Nature, vol. 406, no. 6792, pp. 147-50, Jul 13 2000, doi: 10.1038/35018000. 
5. J. P. Lefaucheur et al., "Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS)," (in English), Clinical neurophysiology : official journal
of the International Federation of Clinical Neurophysiology, vol. 125, no. 11, pp. 2150-2206, Nov 2014, doi: 10.1016/j.clinph.2014.05.021. 
6. B. Heng, S. B. Ahn and A. Guller, "TMS-like Magnetic Fields Modulate Metabolic Activity of Hepatic and Colorectal Cancer Cells." IEEE Transactions on Magnetics: 1-1, doi:
10.1109/tmag.2022.3147219.

Beyond conventional neurostimulation: effects of TMS like magnetic fields on cells and nanomaterials and their potential applications in oncology and regenerative medicine

The continuous growth in the demand to store, process, and access data is one of the main drivers of spintronic research. Emerging big data and AI computing technologies require writing data in less time and storing them at a smaller scale, and consuming less energy [1]. Magnetic memories (MRAM) using spin-transfer torques have proven their place among leading non-volatile memory technologies and are currently in production for eFlash replacement applications [2]. In parallel, spin-orbit torques (SOT) have emerged and proven to be an efficient way of writing reliably magnetization at nanosecond time scale, broadening the scope of MRAM to applications that run close to the clock speed of the central processing unit, leading to novel spintronic memory and computing approaches [3], [4].
I will review across this presentation the fundamental characteristics of SOT and their use to switch perpendicularly magnetized magnetic tunnel junction (MTJ) devices. I will cover different challenges to take up SOT-MRAM from material and stack optimization to technology large-scale integration and circuit design [5]. After describing typical full-scale integration process of SOT-MRAM devices on 300mm wafers using CMOS compatible processes, I will discuss manufacturable field free methods and figures of merit for SOT-based memories. Finally, I will introduce bit-cell design considerations on scaling and performance in the perspective of circuit macro-design architectures [6], and discuss the interest to combine SOT, STT and voltage-gate (VCMA) effects to improve density and leverage performances [7]. I will conclude with opportunities to diverse SOT-MRAM application spectra, notably in the field of in-memory computing [8]. 

**References:** 

[1] G. Molas and E. Nowak, “Advances in emerging memory technologies: From data storage to artificial intelligence,” Appl. Sci., vol. 11, no. 23, (2021), [2] B. Dieny et al., “Opportunities and challenges for spintronics in the microelectronics industry,” Nat. Electron., vol. 3, no. 8, pp. 446–459 (2020), [3] Q. Shao et al., “Roadmap of Spin-Orbit Torques,” IEEE Trans. Magn., vol. 57, no. 7 (2021), [4] A. Manchon et al., “Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems,” Rev. Mod. Phys., vol. 91, no. 3 (2019), [5] K. Garello, F. Yasin, and G. S. Kar, “Spin-orbit torque MRAM for ultrafast embedded memories: From fundamentals to large scale technology integration,” IEEE IMW 2019, pp. 2019–2022 (2019), [6] M. Gupta et al., “High-density SOT-MRAM technology and design specifications for the embedded domain at 5nm node,” Tech. Dig. - IEDM, vol. 2020-Decem, pp. 24.5.1-24.5.4 (2020), [7] Y. C. Wu et al., “Voltage-Gate-Assisted Spin-Orbit-Torque Magnetic Random-Access Memory for High-Density and Low-Power Embedded Applications,” Phys. Rev. Appl., vol. 15, no. 6, pp. 1–10 (2021), [8] J. Doevenspeck et al., “SOT-MRAM based Analog in-Memory Computing for DNN inference,” Dig. Tech. Pap. - Symp. VLSI Technol., vol. 2020-June, no. 1, pp. 2020–2021 (2020) 

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