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Magnetic elastomers can mechanically deform under a magnetic field. Hard magnetic elastomers can perform more complex motions, but soft magnetic elastomers have a greater magnetoaction. 3D printing, such as Fused Deposition Modeling (FDM), can enhance the magnetoactive properties of magnetic elastomers by creating anisotropy. 3D printing filaments are the stock material for FDM. Recent work has shown that magnetic annealing of magnetic filaments during extrusion creates greater magnetoaction in the filaments. This research studies whether this enhanced performance from magnetically annealed filaments remains once they are extruded through the 3D printing nozzle. The composite samples were made of polyurethane and varying amounts of soft and hard magnetic particulate (carbonyl iron (Fe) and strontium ferrite (SrF)). The composites were extruded into 1.75 mm diameter filaments. Magnetically annealed filaments traveled through a uniform axial magnetic field. Final samples were extruded through a 0.8 mm FDM nozzle into extrudates. The magnetoactive properties were measured by a custom setup, whereby extrudates were hung between electromagnets. Images of samples were captured, overlaid, and analyzed at seven field strengths. The enhanced magnetoactive performance of magnetically annealed filaments was present in the final extrudates, indicating that the magnetic annealing effects were preserved. The higher performance magnetic annealing effects were (1) magnetoaction at lower applied fields for the Fe-containing samples and (2) non-zero magnetoaction in the highest SrF samples. Quantitatively, the least magnetoactive deflection was seen in the highest SrF samples. Mechanical tensile testing data showed that the stiffness of the composite variant increased with a higher percentage of SrF. Magnetically, the samples with more SrF content had lower saturation magnetization (Ms) and higher coercive field (Hc). The high stiffness and magnetic properties contribute to the limited magnetoaction. This approach to magnetic annealing of magnetic elastomers can be used to 3D print accurate and complex components for high-performance soft robotic applications.

MMM 2022

Impact of 3D Printing Extrusion on Magnetically Annealed High Performance Hard/Soft Magnetic Elastomers

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.

Considering the natural abundance of the constituting elements and first-order phase transition (FOPT), LaFe13-xSix-derived compounds have been extensively studied for magnetocaloric effect, a phenomenon that causes the cooling or heating of material when placed in an external magnetic field [1]. They are, however, extremely brittle and mechanically friable, showing rather low thermal conductivities and measurable irreversibility, which thus far could not be eliminated completely. Recently, Pathak et al. [2] reported the first-time discovery of a two-phase, naturally formed at the LaFe2Si stoichiometry rather than LaFe13-xSix compound. LaFe2Si exhibits strongly responsive behaviors without the degradation in properties that can be exploited in weak magnetic fields. However, the phase transition happens rather at low temperatures and the saturation moment is low. We are working on this material to further enhance the phase transition temperature and also to improve the magnetic and mechanical properties of the alloy. In this presentation, we will present the synthesis and characterization of LaFe2-yCoySi. We prepared LaFe2-yCoySi by making the first pre-alloy of FeCoSi and then added Co and melted several times. The alloys were further homogenized by the vacuum suction casting technique, which prepared a 4 to 5 cm long rod with a 6mm diameter of sample. The ferromagnetic to paramagnetic transition temperature increases from 199K for x = 0 to 273K for x = 0.3 and the full width at the half-maximum value of magnetic entropy changes increases significantly with Co doping. We discuss the phase transition, electrical transport, magnetic and magnetocaloric properties of LaFe2-yCoySi compounds.

Phase transition, electrical transport and magnetic entropy change of LaFe2 yCoySi alloys prepared by suction casting

The ability to harness excellent magnetic and optical properties within a heterostructure film composed of a magnetic material and a transition metal dichalcogenide (TMD) semiconductor paves a new pathway for the development of multifunctional sensing devices, information storage technology, etc1. Atomically thin tungsten disulfide (WS2) (thickness â‰¤ 5 nm) has been widely explored as a promising candidate for applications in optoelectronics, spintronics, and valleytronics. The valleytronic property of WS2 can be enhanced when interfacing it with another magnetic material such as iron (Fe), due to the magnetic proximity effect2. However, the growth of this 2D-TMD with controllable thickness, using chemical vapor deposition (CVD), and transferring it onto another substrate (Fe) via a commonly used wet transfer process have remained a challenging task. To overcome this, we employ a combination of pulsed laser deposition (PLD) and sputtering (SP) techniques to grow Fe/WS2 heterostructure films with a controlled interface and desirable magnetic/optical properties. A 5nm thick WS2 film was first grown on MgO substrate using PLD, and a 5nm thick Fe film was then deposited on WS2/MgO using SP. A 2nm thick Ta layer was sputtered on the Fe surface to protect the film from oxidization. X-ray diffraction, Raman and Photoluminescence spectroscopy, and atomic force microscopy confirmed the structure of the heterostructure and the quality of the Fe/WS2 interface. Vibrating sample magnetometry, magneto-optical Kerr effect (MOKE), and magnetic force microscopy indicated that the excellent magnetic properties of Fe are preserved in the Ta/Fe/WS2/MgO heterostructure relative to the Ta/Fe/MgO reference film. MOKE showed a sharp, square magnetic hysteresis loop of Ta/Fe/WS2/MgO with a coercive field (Hc ~ 25 Oe) similar to that of the reference film, Ta/Fe/MgO (Hc ~ 23 Oe). The combined excellent magnetic and optical properties make the Ta/Fe/WS2/MgO heterostructure a promising candidate for a wide range of applications in spintronics, valleytronics, and opto-spincaloritronics3. Our study provides a new, efficient method for the growth of novel 2D van der Waals TMD-based heterostructures with controlled interface properties.

Growth of iron/tungsten disulfide heterostructure films with controlled interface and magnetic properties

Anisotropic magnetoelastic thin films have a significant modification of the acoustic properties near spin reorientation transition (SRT)[1]. These high sensitivity and nonlinearity of the magnetic system have great potential applications in ultrasonic diagnosis and imaging, magnetic sensor and microactuation[2]. In this work, we have prepared FeCoSiB (20 nm)/NiFeCu (10-80 nm) bilayers with induced uniaxial anisotropy on Si substrate by magnetron sputtering, and investigated the magnetization dynamics using a low field ferromagnetic resonance (FMR) technique. As shown in Figure 1, the imaginary permeability spectra gradually split from single to double peaks and then to a single peak, when an opposing magnetic field is applied along the easy axis. Fig. 2 shows the variation of the resonance frequencies with the external magnetic field from -150 to 150 Oe. Although the frequency of the single resonance peak satisfies the linear relation of modified Kittel formula[3,4], the splitting of resonance peaks was not captured in previous work to the best of our knowledge. Independent on the NiFeCu thickness, this splitting always occurs at certain magnetic field near the coercivity, thus, may be attributed to spin reorientation transition (SRT)[5]. In the SRT region, the intensity of the low frequency peak decreases with the increase of the reverse magnetic field, while the intensity of the high frequency peak increases continuously, indicating that the Zeeman interaction compensates the anisotropy. Moreover, the field range of SRT region is related to the thickness of bilayer, the effective magnetization, the exchange coupling constant and the magnetoelastic constants. It is found that the FeCoSiB (20 nm)/NiFeCu (30 nm) bilayer has the maximum SRT magnetic field range, where the NiFeCu layer is expected to be near the SRT thickness. These results provide insights into the design of novel straintronic devices and the understanding of magnetization dynamics of ferromagnetic bilayers.

Ferromagnetic resonance in magnetoelastic NiFeCu/FeCoSiB bilayers near spin reorientation transition

Owing to the relative abundance of its constituent elements and large MCE observed near room temperature, the AlFe2B2 system has attracted much attention recently [1]. As an alternative to current rare earth materials, AlFe2B2 promises the realization of cleaner, energy efficient refrigeration technologies based on phenomena associated with MCE [2]. Additionally, excess Al is believed to generate phase impurities which can change the observed MCE properties of this system [3]. By dissolving certain impurities in acid, a significant enhancement of the MCE properties of this system have been observed [4]. Considering this behavior, we have studied the effect of acid treatment on the magnetic, magnetocaloric, and transport properties of Al0.85+xSi0.15Fe2B2 (x = 0.2, 0.4). The goal was to explore the possibility of enhancing the MCE properties of the materials by adding excess aluminum and subjecting them to acid treatment after annealing. The samples were prepared by arc melting followed by drop-casting. The drop-casted samples were annealed followed by acid treatment. The alloys were characterized by x-ray diffraction, scanning electron microscopy, dc magnetization, and electrical resistivity measurements. The second order ferromagnetic phase transitions were observed near room temperature (~298 K â€“ 315 K) and peak magnetic entropy changes (-Î”SM) of more than 4 J/kg K were observed for a field change of 5 T. The details of phase purity, microstructure, magnetic, and transport properties of the acid treated and the drop casted annealed materials will be presented.

The effect of acid treatment on the magnetic and magnetocaloric properties of Al rich Al0.85+xSi0.15Fe2B2

Magnetic refrigeration is an environmentally friendly cooling technology, which is believed to be significantly more efficient than the currently employed gas-compression-based cooling technologies. The commercialization of this technology is crucially dependent on the discovery of materials that exhibit large magnetocaloric effects and can be easily fabricated using cheap, non-toxic, and readily available elements. The intermetallic Mn1-xFex-Î´NiÎ´Si1-yAly compounds are known to exhibit large magnetocaloric effects at the relatively low magnetic field (H = 2T or lower) and tunable phase transition [1, 2]. These materials have gained much interest in recent years due to the fact that the constituent elements are cheap and readily available. However, selected drawbacks including large thermal hysteresis and mechanical instability make these materials unsuitable for application. More research efforts are required to eliminate these drawbacks so that the application potential for these materials can be realized. Therefore, we have synthesized the substitution of Ni with Co in Mn0.5Fe0.5Ni1-xCoxSi0.94Al0.06 (0.025 â‰¤ x â‰¤ 0.075) alloys by arc melting followed by a rapidly quenched vacuum suction casting technique and study the magnetic and magnetocaloric properties of the system, which has not been reported yet. X-ray diffraction and scanning electron microscopy (SEM) data indicated that the samples exhibited a single-phase. Peak magnetic entropy changes of (â€“ Î”SM) of as-cast alloy with x =0.025 is found to be 12 and 31 J kg-1K-1 for Î”H = 2 and 5 T, respectively around 225 K. The observed large MCEs are due to the first order magneto-structural phase transition exhibited by the materials from low-temperature ferromagnetic orthorhombic phase to high-temperature paramagnetic hexagonal phase. In this presentation, we present details of phase purity, microstructure, and magnetic properties of as-prepared and heat-treated alloys with 0.025 â‰¤ x â‰¤ 0.075

Magnetocaloric properties of Co doped Mn0.5Fe0.5Ni1

The giant magnetocaloric (MC) effect measured in Mn0.5Fe0.5NiSi1-xAlx alloys ( 0.05 Â£ x Â£ 0.07) for a low magnetic field change (|Î”SM|max ~16-24 Jkg-1K-1 at 2 T) [1], and the fact that they are based on cheap and abundant elements motivated the interest on their study. The effect is linked to their first-order martensitic-like magnetostructural transformation (MST) from a high-temperature hexagonal Ni2In-type paramagnetic (PM) phase to a low-temperature orthorhombic TiNiSi-type ferromagnetic (FM) phase which is tunable over wide temperature range by changing the Al content [1,2]. As melt spinning is a rapid solidification technique able to produce alloy ribbon samples with a high chemical homogeneity and may result very appropriate to fabricate these five-elements alloys, we produced Mn0.5Fe0.5NiSi1-xAlx melt-spun ribbons with x=0.055 and 0.060 that were thermally annealed at 1123 K for 4 h; their MST and MC characteristics were studied. RT XRD pattens show that samples are nearly single phase with a major Ni2In-type phase coexisting with a minor amount of the TiNiSi-type one. DSC, M(T)5mT and M(T)2T curves, shown in Fig. 1, denote the occurrence of the MST with a large thermal hysteresis (~ 32 K), the substantial effect of Al-content on the tuning of the MST temperature without a significant change in the magnetization change across the MST which led to similar Â½DSM(T)Â½max values (as Fig. 2 shows). The results are discussed and compared with previous data reported in literature for bulk alloys.

Magnetostructural transition and magnetocaloric effect in thermally annealed Mn0.5Fe0.5NiSi1 xAlx melt

Magnetic refrigeration (MR), exploiting the adiabatic demagnetization phenomena, is preferable over conventional cooling technology due to its high efficiency with environment friendly method [1-3]. Owing to this, the earth-abundant Mn-based alloys, i.e. Mn5Sn3, crystallizes in Ni2In type hexagonal structure (space group P63/mmc), occupies two non-equivalently sites with opposite spin alignment: MnI at 2a site with a moment of 0.8 Î¼B and MnII at 2(d) site with a moment of 3.8 Î¼B and Sn atom occupies 2c site. The temperature and field-dependent dc magnetization measurements have been carried out to study the MCE and exchange bias in Mn5Sn3 alloy. The M (T) curve at 100 Oe shows ordering temperature at Tc ~ 227 K and spin glass (SG) transition at Tg ~ 110 K [Fig. 1a]. The origin of SG is due to geometrical frustration, that comes from vacancy and disordering present at Mn2d site. Furthermore, the M (H) hysteresis loop at 5 K reveals the typical soft ferromagnetic behaviour, saturation magnetisation (MS) of 62 emu/g [Fig.1(b)], where MH loop slightly shifted towards a negative field direction, indicating the presence of exchange bias phenomena with exchange bias field (HEB) 5.67 mT at 50 K. Apart from this, Isothermal magnetic entropy change (Î”SM(T)) is (calculated Using Maxwell equation) 2.16 J/Kg-K at 5 T [Fig. 2], also Î”SM(T) evolve with applied magnetic field as - Î”SM(T) = aHn, where n is local exponent, power law fit gives n = 0.649 (1) [Inset of Fig 2(a)]. From Inset fig. 2(b), It is quite apparent that all the normalized entropy curves with various Î”H values collapse into a single curve, confirming second-order magnetic phase transition. The relative cooling power (RCP) value is obtained as 242 J/kg for a field change of 5 T which is significantly larger than the earlier reported Mn5Sn3 study [4]. Hence, with negligible thermal/magnetic hysteresis and reasonable RCP, the Mn5Sn3 is prominent candidate for MR devices.

Magnetocaloric properties and exchange bias in arc melted Mn5Sn3 alloy

Over the last few decades, interest in discovery of materials that exhibit large magnetocaloric effects below room temperature and can support energy-efficient magnetocaloric liquefaction of various gases is on the rise. Here we report a series of rare-earth based Pr2-xNdxIn compounds, where Curie temperatures are tunable by adjusting xNd between 57 and 110 K. Every member of the family exhibits a sharp magnetic transition between the paramagnetic and ferromagnetic states. These transitions give rise to magnetic field-induced entropy changes comparable to or larger than those reported in any other known material in the same temperature range, making Pr2-xNdxIn compounds suitable for liquefaction of technologically important gases including oxygen, nitrogen, and natural gas. The magnetic transitions in these intermetallics do not show any detectable thermomagnetic hysteresis which is advantageous from the application point of view. While the transition temperature increases with xNd, the maximum entropy change is slightly reduced from 15 J/ Kg K at 57 K when xNd = 0 to 13 J/Kg K at 110 K when xNd = 2, all quoted values are for the magnetic field changing between 0 and 2 T. Notably, the thermodynamic nature of phase transitions for the end-members of the series is different. In case of Pr2In, the transition is first-order magnetoelastic, as evidenced by symmetry-invariant discontinuous changes in cell volume occurring in concert with the ferromagnetic ordering/disordering transitions.1,2 Conversely, the phase transition in Nd2In is rather unconventional, being intermediate between a typical first-order and a typical second-order kind. Density functional theory calculations, providing insights into the electronic structure of the end members and expounding differences in their physical behaviors, will be also discussed. Acknowledgement: This work was performed at Ames National Laboratory (AMES) and was supported by the Division of Materials Science and Engineering of the Office of Basic Energy Sciences of the U.S. Department of Energy (DOE). AMES is operated for the U.S DOE by Iowa State University under Contract No. DE-AC02-07CH11358.

Large reversible magnetocaloric effects in Pr2 xNdxIn

Magnetic refrigeration based on magnetocaloric effect at room temperature is generally considered a potential substitution for classical vapor compression systems due to its high efficiency and environmental friendliness. (MnNiSi)1âˆ’x(Fe2Ge)x materials are attractive multicaloric materials that change their magnetic properties with the application of magnetic field, pressure, and temperature [1],[2]. The effects of electron and proton irradiation techniques in magnetocaloric materials have been reported in peer-reviewed articles therefore, this study investigated the effects of X-ray irradiation on (MnNiSi)1âˆ’x(Fe2Ge)x. Polycrystalline (MnNiSi)1âˆ’x(Fe2Ge)x samples were prepared by arc-melting the constituent elements of purity better than 99.9% in an ultrahigh argon atmosphere to ensure sample homogeneity[2]. The procedure utilized X-RAD 225XL Precision X-Ray. The study evidences an observable effect in the (MnNiSi)1-xFe2Gex,x = 0.34 composition when exposed to an absorbed X-ray dosage of ~120Gy/min for 5 hours. A Quantum Design PPMS was used to measure the magnetization (M) of the (MnNiSi)1âˆ’x(Fe2Ge)x with applied magnetic fields from -3T to 3T. Fig.1(a)shows the M-T data from 200K to 350K with Tc ~ 292K before treatment and 286K after treatment (cooling curve). There was also a significant change in the magnetization ~47.4% from 2.72 emu/g to 4.01 emu/g at an applied magnetic field=100Oe. Fig.1(b)presents the M-H (magnetization vs. magnetic field) loops from 300K to 345K as it exhibited irradiation-induced hysteresis in comparison to the pristine sample. Fig.2(a)exhibits an observable change of 10Oe in the magnetic coercivity at 200K after treatment. Fig.2(b)presents the hysteresis graphs for the samples at 200K and shows a saturation magnetization decrease but yielded an increase in magnetization from H=0Oe-4500Oe for the treated sample. These presented results would provide base guidelines for factors affecting the performance of magnetocaloric materials in extreme environments.

Effect of X Ray Irradiation on Magnetocaloric Material, (MnNiSi)1

In this work, we addressed the fabrication of Ni2MnSn glass-coated microwires (mws) by using the Taylor-Ulitovky technique, as well as their structural, magnetic and magnetocaloric (MC) characterization. Apart from the physical characteristics of the material itself, wire-shaped MC materials bring additional features of interest from the viewpoint of refrigeration applications such as an easier magnetization saturation along wire length, and a large surface-to-volume ratio [1]. The former may lead to reach a given MC effect value at a lower magnetic field change m0Î”H, whereas the latter allows a high heat-transfer rate with the exchange fluid. Microwires were prepared from a bulk arc-melted ingot of nominal composition Ni2MnSn produced from highly pure elements (â‰¥ 99.9 %). Their average metallic core diameter was 86 Âµm (as the inset of Fig. 1(a) shows). Their characteristic XRD pattern, shown in Fig. 1(a), was indexed based on a single-phase austenite with the L21 structure (space group Fm-3m; a= 5.98 Ã…). The foreground graph in Fig. 1(b) shows that the M(T) curves measured upon heating and cooling cycles under magnetic fields m0H of 10 mT, 50 mT, and 1 T almost overlap; austenite shows a Curie temperature of 350 K. The thermal dependencies of the magnetic entropy change -Î”SM(T) for different m0Î”H values are shown at the inset of the figure; the curves are broad reaching a |Î”SM|max value of 2.3 Jkg-1K-1 at 3.0 T. The results are compared with those previously reported for bulk and melt-spun ribbons of the same composition [2,3].

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Impact of 3D Printing Extrusion on Magnetically Annealed High Performance Hard/Soft Magnetic Elastomers

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Phase transition, electrical transport and magnetic entropy change of LaFe2 yCoySi alloys prepared by suction casting

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