Insight into the magnetisation process of martensitic Ni–Mn–Ga films: a micromagnetic and vector magnetometry study

Casoli, F.; Varvaro, G.; Ghahfarokhi, Milad Takhsha; Fabbrici, S.; Albertini, F.

doi:10.1088/2515-7639/abb0ee

Cited by 9 publications

(6 citation statements)

References 43 publications

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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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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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“…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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“…However, such materials can be not only isotropic but also textured. The structures of polycrystals, which originate from single twin crystals of Ni-Mn-Ga alloys and correspond to different textures, are described in many works (see, for example, [15][16][17][18][19]. We will use this information while modeling the behavior of polycrystalline material based on the behavior of single crystals.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Model of Magnetic and Deformation Behavior of Single Crystals and Polycrystals of Ferromagnetic Shape Memory Alloy

Rogovoy

Stolbova

2023

Magnetochemistry

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In this article, a microstructural model of the Heusler alloy with the shape memory effect caused by the application of an external magnetic field is constructed. The dynamics of the magnetization process are described using the Landau–Lifshitz–Gilbert equation. For the numerical implementation of the model using the finite element method, the variational equations corresponding to the differential formulation of the magnetic problem are used. Such an approach makes it possible to reduce (weaken) the requirements for the smoothness of the sought solution. The problem of magnetization of single crystals of the Ni2MnGa alloy, which has a “herringbone”-type martensitic structure (a twinned variant of martensite), is considered. In each element of the twin, the magnetic domains with walls of a certain thickness are formed. The motion and interaction of these walls and the rotation of magnetization vector in the walls and domains under the action of the external differently directed magnetic fields are studied. These processes in the Heusler alloy are also accompanied by the detwinning process. A condition for the detwinning of a ferromagnetic shape memory alloy in a magnetic field is proposed, and the effect of the reorientation (detwinning) of martensitic variants forming a twin on the magnetization of the material and the occurrence of structural (detwinning) deformation in it are taken into account. First, the processes of magnetization and structural deformation in a single grain are considered at different angles between the anisotropy axes of twinned variants and the external magnetic field. For these cases, the magnetization curves are constructed, and the deformed states are identified. The model described such experimental facts as the detwinning process and the jump in magnetization on these curves as a result of this process. It was shown that the jump occurred at a certain magnitude of the strength of the applied external magnetic field and a certain direction of its action relative to the twinning system. Then, based on the obtained results, deformed states arising due to the detwinning process were determined for various (isotropic and texture-oriented) polycrystalline samples, and magnetization curves taking into account this process were constructed for these materials.

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Insight into the magnetisation process of martensitic Ni–Mn–Ga films: a micromagnetic and vector magnetometry study

Cited by 9 publications

References 43 publications

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

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

Microstructural Model of Magnetic and Deformation Behavior of Single Crystals and Polycrystals of Ferromagnetic Shape Memory Alloy

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