United States

High-entropy alloys (HEAs), whose new alloy design concept with multiple principal elements, attracted a lot of attention for structural application and functional aspects. Since their first report in 2004, their compositions have developed from first generation with quinary equiatomic single-phase to second-generation multi-phase structure with non-equiatomic compositions. For magnetocaloric HEAs, their limitations have been recently found to be overcome by using non-equiatomic HEA compositions: GdTbCoAlFe (with Curie temperatures up to 108 K) overcomes the low temperature limit of the rare-earth-containing HEAs (typically saturates around &amp;lt; 60 K) [1,2] and the first-order magnetostructural phase transition in FeMnNiGeSi surpasses the smeared out magnetocaloric effect (MCE) of rare-earth-free HEAs [3,4]. In this work, we further enhance the MCE of non-equiatomic Gd&lt;sub&gt;34.9&lt;/sub&gt;Tb&lt;sub&gt;19.4&lt;/sub&gt;Co&lt;sub&gt;19&lt;/sub&gt;Al&lt;sub&gt;23.3&lt;/sub&gt;Fe&lt;sub&gt;3&lt;/sub&gt; HEA through microstructural control, in which the alloy microwires are annealed using the current density annealing technique. Induced nanocrystals in the amorphous matrix observed from transmission electron microscopy (TEM) are found to increase and grow with the current density magnitude (Fig. 1). This leads to an increase in the working temperature span of the HEA microwires and at the same time offers a relative cooling power (&lt;i&gt;RCP&lt;/i&gt;) comparable to many reported amorphous MCE alloys, both conventional alloys and HEAs (Fig. 2). Our findings pave a pathway for further optimizing MCE through appropriate processing methods on top of careful alloy design selection.

![](https://assets.underline.io/uploads/markdown_image/1/image/fce97f9433fab8f05b035a2bf2ea02e2.jpg)

Fig. 1 TEM results of the (a) as-cast and annealed Gd34.9Tb19.4Co19Al23.3Fe3 microwires using current density values of (b) 50 and (c) 100 x 106 A m-2.

![](https://assets.underline.io/uploads/markdown_image/1/image/a7e0bd8f7ddc93b92bbc79c9201b5616.jpg)

Fig. 2 Literature comparison of RCP as a function of full-width at half maximum (FWHM) for studied microwires (star symbols) versus amorphous conventional alloys (triangles) and HEAs (squares).

2022 Joint MMM-INTERMAG

Enhanced Magnetocaloric Response of High-Entropy Alloy Microwires due to Induced Nanocrystals by Current Annealing

**About**
 The PErvasive Technologies Related to Assistive Environments (PETRA) conference is a highly interdisciplinary conference that focuses on computational and engineering approaches to improve the quality of life and enhance human performance in a wide range of settings, in the workplace, at home, in public spaces, urban environments, and other. Outcomes of this conference have a broad impact in application areas that include, manufacturing, transportation, healthcare, energy systems, security and safety, robotics, biomedicine, environment and conservation, and many others. PETRA brings together very different types of technologies to also address important social and healthcare issues for sensitive populations, such as the elderly, persons suffering from chronic conditions such as Alzheimer’s, Parkinson’s, Cerebral Palsy, and other disabilities or traumas.

 PETRA (which means “stone” in Greek) addresses important human living needs. From a technological perspective, PETRA motivates and inspires new scientific thrusts, innovations and discoveries to improve living environments, a particularly important issue, in an increasingly crowded and complex world where the need for inclusiveness and connectivity with the rest of the world is key. For the elderly in particular, PETRA addresses the fact that, as people grow older; they will increasingly rely on technology to be able to prolong staying in their homes and enjoy an independent life.

 The PETRA 2021 proceedings will be published in the ACM Digital Library as part of the ACM ICPS program. The ISBN number assigned to PETRA '21 is 978-1-4503-8792-7

PETRA 2021

The PErvasive Technologies Related to Assistive Environments (PETRA) conference is a highly interdisciplinary conference that focuses on computational and engineering approaches to improve the quality of life and enhance human performance in a wide range of settings, in the workplace, at home, in public spaces, urban environments, and other. Outcomes of this conference have a broad impact in application areas that include, manufacturing, transportation, healthcare, energy systems, security and safety, robotics, biomedicine, environment and conservation, and many others. PETRA brings together very different types of technologies to also address important social and healthcare issues for sensitive populations, such as the elderly, persons suffering from chronic conditions such as Alzheimer’s, Parkinson’s, Cerebral Palsy, and other disabilities or traumas.

High-entropy alloys (HEAs), whose new alloy design concept with multiple principal elements, attracted a lot of attention for structural application and functional aspects. Since their first report in 2004, their compositions have developed from first generation with quinary equiatomic single-phase to second-generation multi-phase structure with non-equiatomic compositions. For magnetocaloric HEAs, their limitations have been recently found to be overcome by using non-equiatomic HEA compositions: GdTbCoAlFe (with Curie temperatures up to 108 K) overcomes the low temperature limit of the rare-earth-containing HEAs (typically saturates around &lt; 60 K) [1,2] and the first-order magnetostructural phase transition in FeMnNiGeSi surpasses the smeared out magnetocaloric effect (MCE) of rare-earth-free HEAs [3,4]. In this work, we further enhance the MCE of non-equiatomic Gd34.9Tb19.4Co19Al23.3Fe3 HEA through microstructural control, in which the alloy microwires are annealed using the current density annealing technique. Induced nanocrystals in the amorphous matrix observed from transmission electron microscopy (TEM) are found to increase and grow with the current density magnitude (Fig. 1). This leads to an increase in the working temperature span of the HEA microwires and at the same time offers a relative cooling power (RCP) comparable to many reported amorphous MCE alloys, both conventional alloys and HEAs (Fig. 2). Our findings pave a pathway for further optimizing MCE through appropriate processing methods on top of careful alloy design selection.

![](https://assets.underline.io/uploads/markdown_image/1/image/fce97f9433fab8f05b035a2bf2ea02e2.jpg)

Fig. 1 TEM results of the (a) as-cast and annealed Gd34.9Tb19.4Co19Al23.3Fe3 microwires using current density values of (b) 50 and (c) 100 x 106 A m-2.

![](https://assets.underline.io/uploads/markdown_image/1/image/a7e0bd8f7ddc93b92bbc79c9201b5616.jpg)

Fig. 2 Literature comparison of RCP as a function of full-width at half maximum (FWHM) for studied microwires (star symbols) versus amorphous conventional alloys (triangles) and HEAs (squares).

technical paper

The 15th Joint MMM-INTERMAG Conference (2022 Joint) 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 plenary session, and an evening session, with about 1500 presentations overall. 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 2022 Joint Conference will offer both in-person and prerecorded on-demand content.

For tickets to the event, please register at the following link: https://magnetism.org/register

Please register for the Joint MMM-Intermag conference to join the event.

This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

Non-collinear antiferromagnetic orders are of strong interest in the fields of spintronics, topological magnetism and multiferroicity [1]. However, the magnetic imaging of these materials is particularly challenging due to their zero net magnetization. Dy epitaxial films exhibit an antiferromagnetic helical phase and strong X-ray magnetic scattering at the Dy L3 edge [2] These characteristics make it a perfect candidate to fully vectorial reconstruction of a non-collinear magnetic order, enabled by the new combination of Resonant X-ray Magnetic Scattering (RXMS) [3] and Coherent Diffraction Imaging (CDI) [4]. In order to implement this technique, micro-objects are required as model samples. The micropatterning of Dy nanofilms (top-down approach) is however particularly challenging due to the high reactiveness of Dy. In this work, we present the results of this microfabrication process, from the growth of Dy epitaxial nanofilms to the patterning and full characterization of the µ-disks. The high crystalline quality of the Dy(0001) films, grown on A-plane sapphire/(110) Nb templates, is kept after the optical lithography followed by Ion Beam Etching. X-ray diffraction (Fig.1) indicates a moderate decrease in coherence length (10%) and an increase in mosaicity (17%) in 2 mm disks compared with continuous films. However, an FCC phase is formed, likely due to hydrogenation during the patterning process [5] SQUID measurements and RXMS (BM28-ESRF) confirm the occurrence of the helical phase in the Dy µ-disks, with similar Néel and Curie temperatures as in continuous films, but with a slight increase in critical fields. The temperature dependence of (002-t) magnetic satellites reveals that helical turn angles in the patterned samples do not differ significantly from those observed in epitaxial films [6](Fig. 2). The effect of the buffer layer (Nb or Nb/Y) is also studied and correlated to the role of epitaxial strains.

![](https://assets.underline.io/uploads/markdown_image/1/image/8129cbfe6c8f62f2fcbd865b2993bdcd.jpg)

(0 0 L) scans at the Dy L3 edge at 130 K measured for Nb/Dy (green), Nb/Y/Dy (orange) and their respective µ-disks. Grey region indicates the magnetic satellites. Insert: SEM tilted view of Dy µ-disks.

![](https://assets.underline.io/uploads/markdown_image/1/image/45d553476adcd2f5d6198955784f0389.jpg)

Turn angle of the Dy helical phase as a function of temperature (same samples as in Fig.1).

Development of Dy µ-disks for imaging of helimagnetic domains

Spin glasses, generally defined as disordered systems with randomized competing interactions that result in an extensively degenerate ground state1, 2, are a widely investigated complex system. Theoretical models describing spin glasses are broadly used in other complex systems, such as those describing brain function3, error-correcting codes4, or stock-market dynamics5. This wide interest in spin glasses provides strong motivation to generate an artificial spin glass within the framework of artificial spin ice systems6. Here, we present the first experimental realization of an artificial spin glass, consisting of dipolar coupled single-domain Ising-type nanomagnets arranged onto an interaction network that replicates the aspects of a Hopfield neural network7. Using cryogenic x-ray photoemission electron microscopy (XPEEM), we performed temperature dependent imaging of thermally driven moment fluctuations within these networks and observed characteristic features of a two-dimensional Ising spin glass. Specifically, the temperature dependence of the spin glass correlation function follows a power law trend predicted from theoretical models on two-dimensional spin glasses. Furthermore, we observe clear signatures of the hard to observe rugged spin glass free energy1 in the form of sub-aging, out of equilibrium autocorrelations1 and a transition from convergent to divergent dynamics1, 8.

![](https://assets.underline.io/uploads/markdown_image/1/image/b3ae2199ab934834ddc1bb2571df82f4.jpg)

Direct observation of a Dynamical Glass Transition in a Nanomagnetic Artificial Hopfield Network

The MnTX (T = Ni, Co; X = p-block elements) compounds have received considerable attention due to the coupled first-order magnetic and structural phase transitions (MST) they exhibit. Large magnetocaloric effects are often associated with these phase transitions. The Mn1-xFexNiSi1-yAly system is a member of the MnTX family for which a large magnetic entropy change of 23 J kg-1 K-1 has been reported at T= 210K, ΔH = 2T. This value was reported for x = 0.5, y = 0.07 and for x = 0.5, y = 0.05 the peak value decreased to 17 J kg-1 K-1 (T = 315K, ΔH = 2T) (Biswas et. al. Acta Mat. 180 (2019) 341). For x = 0.4, y = 0.7, a peak magnetic entropy change of 9.3 J kg-1 K-1 was recently observed near 247 K (Ghosh et. al. JMMM 500 (2020) 166345). These studies suggested that the Mn1-xFexNiSi1-yAly system exhibits the maximum entropy change for x = 0.5. It is interesting to study the effect of Fe and Ni concentration variation on the magnetocaloric properties of the Mn0.5Fe0.5-xNi1-xSi1-yAly, which has not been reported yet. Therefore, in this work, we present an experimental study on the effects of partially replacing Fe with Ni on the structural, magnetic, and magnetocaloric properties of Mn0.5Fe0.5-xNi1+xSi0.94Al0.06 (0.025 ≤ x ≤ 0.10). The results of x-ray diffraction and scanning electron microscopy (SEM) showed that the samples exhibited a single-phase and energy dispersive spectroscopy analysis showed that the resulting compositions were close to the nominal compositions. Maximum magnetic entropy changes of – ΔSM = 22 and 57 J kg-1K-1 for ΔH = 2 and 5 T, respectively have been realized for x = 0.1 around 322 K. The observed large MCEs are due to the MST exhibited by the materials from low-temperature FM orthorhombic phase to high-temperature PM hexagonal phase. Work at SUNY, Buffalo State was supported by the startup fund from SUNY Buffalo State College and Undergraduate Summer Research Fellowship award, Undergraduate Research Office, Buffalo State.

The variation of Fe/Ni concentration and its effect on the magnetic and magnetocaloric properties of Mn0.5Fe0.5-xNi1+xSi0.94Al0.06

The M5XB2 materials system has been widely studied as permanent magnetic materials[1] [2]. As permanent magnetic materials, their coercivity and magnetic energy product are lower than those of the mainstream permanent magnetic materials. Xie et al.[3] and Cedervall et al.[4] proposed that the Mn5PB2 and (Fe1-xCox)5PB2 compounds have the prospect of being applied as magnetocaloric materials due to their near room temperature Curie temperature. In this work, the structure and magnetocaloric properties of the Mn5(SiP)B2 compounds of the M5XB2 material system were studied. According to a refinement of the XRD data the Mn5(Si1-xPx)B2 compounds all crystallize in the Cr5B3–type body-centered tetragonal structure, with a small amount of Mn2P as a secondary phase (less than 7%). The lattice parameters and the unit-cell volume of the compounds change linearly with the increase in P content. These experimental results are consistent with calculated DFT results. The Curie temperature of the compounds can continuously be adjusted between 305 and 411 K by changing the Si/P ratio. The introduction of P also caused a decrease in saturation magnetization. The magnetic phase transition of these compounds was determined using Arrot plots and the field exponent n for the magnetic entropy change based on Landau's theory. The studied compounds all show a second-order magnetic phase transition. Since the compounds show a second-order phase transition, the magnetic entropy change caused by the phase transition was not large: 1.9 and 1.4 J/kgK for Mn5SiB2 and Mn5PB2, respectively. However, the advantage of this series of compounds is that the Curie temperature can be adjusted continuously around room temperature.

![](https://assets.underline.io/uploads/markdown_image/1/image/1d9940cac68d7c5951d382a4b1969178.jpg)

Fig. 1. Temperature dependence of magnetization of Mn5(Si1-xPx)B2(0 ≤ x ≤ 1) in a field of 0.01T.


![](https://assets.underline.io/uploads/markdown_image/1/image/a3a6abe7d32a72ba069affbbfed1f01d.jpg)

Fig. 2. TC as a function of P content for Mn5(Si1-xPx)B2 (0 ≤ x ≤ 1).

Magnetocaloric Properties of a New Type of Magnetocaloric Materials - M5XB2 System

La(Fe, Si)13 is a promising candidate for magnetocaloric based technology such as magnetic refrigeration or energy harvesting [1-3]. This alloy family consists of a low content of rare earth (7.1 at. %) and high content of iron, resulting in a cheap and non-toxic compound. La(Fe, Si)13 based alloys exhibit a large magnetocaloric effect (MCE) at the transition between ferromagnetic and paramagnetic states, which occurs at Curie temperatures (Tc) ranging between 200-259K [4]. The magnetic properties (Tc, magnetization, MCE), the crystal structure (cubic or tetragonal) and the type of transition can be tuned by adjusting the Si content. Furthermore, the Curie temperature can be increased to above room temperature by doping and hydrogenation [5]. Recently our group reported for the first time the possibility to fabricate thick films of La(Fe, Si)13 [6]. Here we present a study on compositionally graded films of La-Fe-Si. The films were fabricated by triode co-sputtering of three targets (La-Fe, Fe, Si-Fe) onto thermally oxidised stationary Si substrates (100 mm in diameter). The composition of the as-deposited films was mapped by EDX, as shown in Fig. 1. The films were annealed ex-situ in a rapid thermal annealing furnace at 900°C. For each film, we selected samples from specific regions for characterization using optical and scanning electron microscopy, VSM-SQUID magnetometry and X-ray spectroscopy. Fig. 2 displays M(T) measurements on four La-Fe-Si samples of 5 μm thickness, taken from the regions specified in Fig. 1. The presentation will report results from films of nominal thickness ranging between 150nm – 5μm. The presentation will give details about how the structural and magnetic properties vary as a function of film composition, thickness and annealing conditions. Prospects for further developments and possible applications will also be discussed. Acknowledgement: This research has received funding from the French National Research Agency under the HiPerTherMag project (ANR-18-CE05-0019).

![](https://assets.underline.io/uploads/markdown_image/1/image/e47b4016b72ccd38f00fea3375cd00d9.jpg)

![](https://assets.underline.io/uploads/markdown_image/1/image/a06f84bea07fbcfb4eb5845d9b87a6ea.jpg)

Compositionally graded La-Fe-Si films

Compositionally graded La-Fe-Si films

The LaFe13-xSix compounds have been studied for nearly two decades for their potential to serve as materials for magnetocaloric cooling. They exhibit either first- or second-order phase transitions depending on x(Si). Here we present the discovery of a naturally formed two-phase composite at the LaFe2Si stoichiometry, which exhibits strongly responsive behaviors without mechanical degradation that can be exploited in weak magnetic fields. Some of the unusual properties include a two-step, nearly anhysteretic first-order phase transformation between ferromagnetic (FM) and paramagnetic (PM) states, instead of a singular phase change present in conventional LaFe13-xSix, that is preserved in magnetic fields as high as 100 kOe. In addition to the giant magnetocaloric effect, the title material exhibits large, plateau-like positive magnetoresistance, both extending over a much wider temperature range when compared to phase-pure LaFe13-xSix. Finally, the composite also shows a Griffiths-like phase associated with short-range FM clustering in the PM state (Pathak et. al., Acta Mat. 215 (2021) 117083). We will also discuss the effect of impurities on magnetic, magnetocaloric, and transport behaviors of LaFe2Si. The work at Ames Laboratory was supported by the Division of Materials Science and Engineering, the Office of Basic Energy Sciences of the DOE. Ames Laboratory is operated for the U.S DOE by Iowa State University under Contract No. DE-AC02-07CH11358. Work at SUNY, Buffalo State was supported by the startup fund from SUNY Buffalo State College and the Undergraduate Research Office, Buffalo State.

Unusual magnetic, magnetocaloric, and transport properties in phase-separated LaFe2Si

High-entropy alloys (HEAs), based on the design concept of mixing five or more principal elements to yield high entropy of mixing (ΔSmix), expands the compositional space of multicomponent materials when compared to conventional materials, which are mainly based on one or two main constituents. HEAs, thus, form compositions without dominant elements, in which new materials with excellent properties, some of them being superior or unique compared to the conventional materials, have been found [1]. These advantages prompted a large surge in studying HEAs, with the explored compositions evolving from first-generation single phase equiatomic to second-generation multiphase non-equiatomic HEAs. The latter are recently reported with properties that outdo those of the first-generation HEAs, such as excellent strength-ductility combination, surpassing the low temperature limit, or enhanced magnetocaloric properties of rare-earth-free high-entropy alloys owing to a first-order magnetic phase transition [1-3]. Here, we present, when tuning CoCrMnNiTi alloys from conventional to the high-entropy region (i.e. ΔSmix &gt; 1.5 R, where R is the gas contstant, 8.314 J mol-1 K-1), the evolution of their thermomagnetic and magnetocaloric behavior. The obtained HEA has a martensitic temperature tuned nearer to room temperature and a 10% increase in the entropy change (Fig. 1). This work demonstrates the recently proposed claim [1-3] that it is possible to obtain high-performance magnetocaloric materials within the HEA compositional space. Work supported by AEI/FEDER-UE (grant PID2019-105720RB-I00), US/JUNTA/FEDER-UE (grant US- 1260179), Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía (grant P18-RT-746), Army Research Laboratory under Cooperative Agreement Number W911NF-19-2-0212 and Sevilla University under VI PPIT-US program.

![](https://assets.underline.io/uploads/markdown_image/1/image/ac398a967db02e43d38fa8ceed0d87a5.jpg)

Fig 1. The variation of martensitic transition temperatures (square symbols) and entropy change at the transition (circular symbols) after tuning a conventional alloy towards the high-entropy region (ΔSmix > 1.5 R).

Tuning conventional alloys towards the high-entropy space: thermomagnetic and magnetocaloric behavior

Magnetic refrigeration is an energy-efficient, environmentally-friendly alternative to conventional vapor-compression cooling technology. There are several magnetic cooling device designs in existence today that are potentially commercially viable, on condition that that suitable working materials can be developed. This challenge is unresolved due to issues associated with shaping the mostly brittle magnetocaloric alloys into thin-walled channeled regenerator structures to facilitate efficient heat transfer between the solid refrigerant and the heat exchange fluid in an active magnetic regenerator (AMR) cooling device. To address these challenges, we have developed an extrusion-based additive manufacturing (AM) method to 3D print porous magnetocaloric structures.1 This AM technique’s novelty lies in the initial material feedstock comprising of magnetic particles (upto ~ 85 wt%) and sacrificial polymer binders dispersed in a multi-solvent system. While the solvents control the ink rheology, the polymers bind the magnetic particles, enabling retention of the regenerator architecture. Next, a two-step sintering process removes the binder and subsequently promotes grain growth and densification of the final finished part. Research efforts involving La0.6Ca0.4MnO3 nanoparticles will be presented. Figure 1 shows that the magnetocaloric response (indicated by the magnetic entropy change) of the 3D printed test scaffold is only ~17% lower than that of the precursor particles. Spatially designed structures with channel dimensions of 150 µm were obtained to exhibit the effectiveness of this fabrication process. The microstructures and porosity of the as-printed and sintered samples will be discussed in the context of results obtained via 3D X-ray computed tomography. Overall, this study provides strategies for realizing low-cost magnetic regenerators, thus potentially eliminating one of the main barriers to commercialization of magnetic cooling technology.

![](https://assets.underline.io/uploads/markdown_image/1/image/40b0fbbd914b91dd6f4cee2961b48796.jpg)

Extrusion-Based 3D Printing of Magnetocaloric Structures

The possibility of inducing a structural martensitic transformation by applying a magnetic field in meta-magnetic shape memory alloys gives rise to interesting properties such as magnetic actuation, giant magnetoresistance, or giant inverse magneto-caloric effect, which make these alloys very attractive for practical applications in sensing and magnetic refrigeration. Composites made from polymer matrix with meta-magnetic shape memory powder have been recently proposed to overcome the intrinsic brittleness of the bulk alloys. This, in fact, opens the possibility of the use of particles for additive manufacturing purposes. The production, characterization, and optimization of the properties of powder particles are therefore milestones to get valuable functional composites. In the present work, the martensitic transformation and the magnetic properties of Ni45Co5Mn37In13 powder microparticles obtained by ball milling have been studied. Even for very large milling times, a considerable dispersion in the particle size is observed in all the samples. Nevertheless, it is found that the characteristic of the transformation and the magnetic response is exactly the same in those particles with the same particle size, irrespective of the milling time. A direct correlation between size and deformation can be then established, from which the effect of mechanically induced microstructural defects on the magnetism is analyzed. The effect of mechanically induced defects on the magnetocaloric effect and the viability of the use of the studied microparticles for composite elaboration are also analyzed. Polymer composites have been elaborated by embedding the micro/nanoparticles in a mixture of polylactic acid(PLA) and poly-caprolactone(PCL). In order to get 3D printable wires with optimum mechanical properties and good magnetic response, the particles size, polymers fractions, and particles concentration have been varied. The magnetic response and printability of the obtained filaments have also been studied.

![](https://assets.underline.io/uploads/markdown_image/1/image/4c365c47c2173f24fd05b88fc85de5e6.jpg)

Multifunctional magnetic composites based in meta-magnetic shape memory alloys for 3D printing applications

Multifunctional magnetic composites based in meta-magnetic shape memory alloys for 3D printing applications

The use of composites combining a thermoplastic and functional fillers for additive manufacturing (AM), as in fused deposition modeling, FDM, provides a path for low cost development of functional parts with complicated geometries [1]. Magnetic refrigeration requires refrigeration beds with intricate geometries for the passage of the heat transfer fluid. Heusler alloys exhibiting magneto-structural transformation (MST) are attracting enormous attention as they can show a large response without relying on critical elements [2]. However, machinability of these alloys is compromised, making AM attractive for the fabrication of the refrigerator beds. Off-stoichiometry Ni2MnGa Heusler powder has been obtained by ultrasonic atomization, resulting in spheric particles subsequently sieved at 100 μm (Fig. 1). Differential scanning calorimetry (DSC) enabled to identify the MST in the atomized Heusler alloy (Fig. 2(a)). This powder was used to fill customized PLA capsules that were used as the feedstock for the extrusion of composite filaments for FDM according to the method showed in Ref. [3]. Composite filaments were manufactured with different concentrations of fillers ranging from 30 to 64 wt. %, determined by thermogravimetric analysis, TGA, (Fig. 2(b)). As the particles were not subjected to high temperatures during the extrusion of the filaments (less than 200 °C) , the phases present in the alloy do not change. The AM of magnetocaloric parts can avoid the shape limitation and, in this case, the polymer matrix would prevent the weakening of the structure due to the successive volume changes taking place with the cyclical occurrence of an MST. Work supported by AEI/FEDER-UE (grant PID2019-105720RB-I00), US/JUNTA/FEDER-UE (grant US-1260179), Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía (grant P18-RT-746), Army Research Laboratory under Cooperative Agreement Number W911NF-19-2-0212 and POB “Technologie Materialowe” of Warsaw University of Technology within the Excellence Initiative: Research University (IDUB) program.

![](https://assets.underline.io/uploads/markdown_image/1/image/4e2d2b38f53f80505a1d801ab989ac98.jpg)

Fig. 1. Scanning electron micrograph of Ni2MnGa powder.

![](https://assets.underline.io/uploads/markdown_image/1/image/50cf44b9c97b07a7d8704c2818ad4355.jpg)

Fig. 2. (a) DSC results of Heusler powder and (b) TGA curves of raw PLA and PLA-based composite filaments.

Enhanced Magnetocaloric Response of High-Entropy Alloy Microwires due to Induced Nanocrystals by Current Annealing

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