Influence of martensitic configuration on hysteretic properties of Heusler films studied by advanced imaging in magnetic field and temperature

Ghahfarokhi, Milad Takhsha; Chirkova, Alisa; Maccari, Fernando; Casoli, F.; Ener, Semih; Skokov, Konstantin; Cabassi, R.; Gutfleisch, Oliver; Albertini, F.

doi:10.1016/j.actamat.2021.117356

Cited by 5 publications

(4 citation statements)

References 60 publications

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“…[ 31,34 ] In Ni–Mn–Ga, twin boundaries are slightly tilted and rotated away from {110} planes (as described before) and from the six possible orientations in bulk, in these films we only observe the so‐called type X subsets, where the twin boundary is inclined by 45° to the substrate normal and traces follow either [100] Ni–Mn–Ga or [010] Ni–Mn–Ga directions on the film surface. [ 31,35 ] Twin boundaries in (i) are rotated by 45° with respect to those visible in (g) and (h) due to the differences in the substrate architecture mentioned before (Figure 2d–f). Due to the four‐fold symmetry of the cubic substrates, two equivalent orientations of the parallel lines on the film surface are possible, which are also clearly visible for both films grown on Si.…”

Section: Resultsmentioning

confidence: 90%

Integration of Multifunctional Epitaxial (Magnetic) Shape Memory Films in Silicon Microtechnology

Fink,

Kar,

Lünser

et al. 2023

Adv Funct Materials

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Magnetic shape memory alloys exhibit various multifunctional properties, which range from high stroke actuation and magnetocaloric refrigeration to thermomagnetic energy harvesting. Most of these applications benefit from miniaturization and a single crystalline state. Epitaxial film growth is so far only possible on some oxidic substrates, but they are expensive and incompatible with standard microsystem technologies. Here, epitaxial growth of Ni–Mn–based Heusler alloys with single crystal‐like properties on silicon substrates is demonstrated by using a SrTiO3 buffer. It is shown that this allows using standard microfabrication technologies to prepare partly freestanding patterns. This approach is versatile, as its applicability for the NiTi shape memory alloy is demonstrated and spintronic and thermoelectric Heusler alloys are discussed. This paves the way for integrating additional multifunctional effects into state‐of‐the‐art microelectronic and micromechanical technology, which is based on silicon.

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Section: Resultsmentioning

confidence: 90%

Integration of Multifunctional Epitaxial (Magnetic) Shape Memory Films in Silicon Microtechnology

Fink,

Kar,

Lünser

et al. 2023

Adv Funct Materials

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“…The AFM images in Figure 1a demonstrate the presence of X-type twins that are characterized by different orientations of the twinning planes (i.e., at 45 • degrees to the MgO(001) substrate) [42][43][44][45][46][47]. The corresponding out-of-plane contribution of the magnetic domains can be visualized in the MFM images as the dark and the bright contrasts (Figure 1b) [42][43][44][45][46][47][48][49]. When cooling from 400 K, the thermomagnetic curves of the pristine sample (Figure 1c) show an abrupt rise in the susceptibility at around 344 K, which is ascribed to crossing the austenitic Curie temperature of the sample [50], where it transforms from the paramagnetic austenitic phase to ferromagnetic austenitic phase.…”

Section: Resultsmentioning

confidence: 99%

Dewetting Process in Ni-Mn-Ga Shape-Memory Heusler: Effects on Morphology, Stoichiometry and Magnetic Properties

et al. 2022

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In this work, dewetting process has been investigated in shape-memory Heuslers. To this aim, series of high-temperature annealing (1100–1150 K) have been performed at high vacuum (time is varied in the range of 55–165 min) in Ni-Mn-Ga epitaxial thin films grown on MgO(001). The process kinetics have been followed by studying the evolution of morphology and composition. In particular, we report the initiation of the dewetting process by the formation of symmetric holes in the films. The holes propagate and integrate, leaving micrometric and submicron islands of the material, increasing the average roughness of the films by a factor of up to around 30. The dewetting process is accompanied by severe Ga and Mn sublimation, and Ni-Ga segregation, which significantly modify the magnetic properties of the films measured at each stage. The annealed samples show a relatively weak magnetic signal at room temperature with respect to the pristine sample.

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“…Coherently, the high-resolution backscattered electron (BSE) image in Figure d shows the dominant presence of Y-type twining configurations and the small regions of X-type twining configurations, some of which are labeled in the figure. X-type and Y-type are characterized by different orientations of the twins (i.e., at 45° and 90° degrees to the MgO(001) substrate, respectively) in the martensitic phase. − As a consequence, they are also characterized by different magnetic anisotropy contributions, all in-plane for the Y-type and both in-plane and out-of-plane for the X-type. The blurred regions in Figure d are expected to be due to the material undergoing the martensitic transition at room temperature.…”

Section: Results and Discussionmentioning

confidence: 99%

“…The blurred regions in Figure d are expected to be due to the material undergoing the martensitic transition at room temperature. Comprehensive structural and microstructural characterizations can be found in references. ,− …”

Section: Results and Discussionmentioning

confidence: 99%

Magnetic Shape-Memory Heuslers Turn to Bio: Cytocompatibility of Ni–Mn–Ga Films and Biomedical Perspective

Takhsha,

Furlani,

Panseri

et al. 2023

ACS Appl. Bio Mater.

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Magnetic shape-memory (MSM) Heuslers have attracted great attention in recent years for both caloric and magnetomechanical applications. Thanks to their multifunctional properties, they are also promising for a vast variety of biomedical applications. However, this topic has been rarely investigated so far. In this communication, we present the first report on the absence of cytotoxicity of MSM Heuslers in Ni−Mn−Ga epitaxial thin films and the perspective toward bioapplications. Qualitative and quantitative biological characterizations reveal that Ni−Mn− Ga films can promote the adhesion and proliferation of human fibroblasts without eliciting any cytotoxic effect. Additionally, our findings show that the morphology, composition, microstructure, phase transformation, and magnetic characteristics of the films are well preserved after the biological treatments, making the material a promising candidate for further investigations.

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Influence of martensitic configuration on hysteretic properties of Heusler films studied by advanced imaging in magnetic field and temperature

Cited by 5 publications

References 60 publications

Integration of Multifunctional Epitaxial (Magnetic) Shape Memory Films in Silicon Microtechnology

Integration of Multifunctional Epitaxial (Magnetic) Shape Memory Films in Silicon Microtechnology

Dewetting Process in Ni-Mn-Ga Shape-Memory Heusler: Effects on Morphology, Stoichiometry and Magnetic Properties

Magnetic Shape-Memory Heuslers Turn to Bio: Cytocompatibility of Ni–Mn–Ga Films and Biomedical Perspective

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