Martensitic transformation in Ni2MnGa films: A ferromagnetic resonance study

Dubowik, J.; Kudryavtsev, Y. V.; Lee, Y. P.

doi:10.1063/1.1641956

Cited by 29 publications

(12 citation statements)

References 25 publications

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“…For the austenite phase we observe a very narrow hysteresis curve with a small coercive field of H C,Aust = 2 mT, whereas the hysteresis of the martensite phase becomes much broader yielding a coercive field of H C,Aust = 10 mT. Such a change of the shape of the magnetic hysteresis as well as the increase of the coercive field were also found in literature for Ni 2 MnGa [17]. These changes can be explained by the structural phase transition, since it is accompanied by a substantial change of the magnetic anisotropy (see Sec.V).…”

Section: A Characterizationsupporting

confidence: 70%

Element-specific electronic structure and magnetic properties of an epitaxialNi51.6Mn32.9Sn15.5thin film at the austenite-martensite transition

et al. 2015

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An austenite-martensite transition was observed in a 100-nm-thick Ni 51.6 Mn 32.9 Sn 15.5 film by temperaturedependent resistivity and magnetization measurements, revealing a martensite starting temperature of M S ≈ 260 K. The influence of the structural phase transition on the electronic structure and the magnetic properties was studied element specifically employing temperature-dependent x-ray-absorption spectroscopy and x-ray magnetic circular dichroism. In addition, density functional theory calculations have been performed to study the electronic and magnetic properties of both phases. It is shown that off-stoichiometric Ni-Mn-Sn alloys can exhibit a substantial magnetocrystalline anisotropy energy in the martensite phase. For Mn a change of the electronic structure and a strong increase of the ratio of orbital to spin magnetic moment m l /m S can be observed, whereas for Ni nearly no changes occur. Applying an external magnetic field of B = 3 T reverses the change of the electronic structure of Mn and reduces the ratio of m l /m S from 13.5 to ≈1 % indicating a field-induced reverse martensitic transition.

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Section: A Characterizationsupporting

confidence: 70%

Element-specific electronic structure and magnetic properties of an epitaxialNi51.6Mn32.9Sn15.5thin film at the austenite-martensite transition

et al. 2015

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“…The extrapolated to T = 0 K value of 4πM eff ≈ 12 − 3.2 ≈ 8.8 kGs (M ef f ≈ 700 Gs). This value is in a good agreement with the theoretically predicted magnetization with the magnetic moment of 4 µ B per Mn atom [8] and is the highest among similar HA films exhibiting shape memory effect [7]. In the course of H r vs. T there are small anomalies indicated by arrows in Fig.…”

Section: Experimental Results and Their Discussionsupporting

confidence: 79%

“…On the other hand, the lack of clear signs of MT in the films may result from their clamping from the substrates since the films are usually constrained by the substrates. FMR has been shown useful for tracing structural transformations in thin HA films [7]. We extensively used FMR to reveal MT in our Ni-Mn-Sn films.…”

Section: Experimental Results and Their Discussionmentioning

confidence: 99%

Martensitic Transformations and Magnetic Properties of Ni-Mn-Sn Heusler Alloy Films

2008

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We report on structural and magnetic properties of Ni50Mn50−xSnx (x = 12 ÷ 14) films and compare them with those of the bulk Ni-Mn-Sn alloys. Magnetic measurements reveal clear presence of martensitic transformation in bulk alloys but in the flash-evaporated Ni-Mn-Sn thin films martensitic transformation is usually less visible. The best film samples annealed for 1 h at about 900 K exhibit clear signs of martensitic transformation: i.e., a small defect in magnetization and a substantial increase in ferromagnetic resonance line width.

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“…While combinatorial studies provide ample information, including the stability range of the martensite phase and ferromagnetic ordering, the substrate constrains the films, thus shifting phase boundaries. Further Ni‐Mn‐Ga film fabrication methods include pulsed laser deposition,132, 133 laser beam ablation,134 flash evaporation of alloy powders,135 and multi‐dipolar plasma‐assisted sputtering, which may be performed with multiple alloy targets 136…”

Section: Three‐dimensional Aggregates and Constructsmentioning

confidence: 99%

Size Effects on Magnetic Actuation in Ni‐Mn‐Ga Shape‐Memory Alloys

2010

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The off-stoichiometric Ni(2)MnGa Heusler alloy is a magnetic shape-memory alloy capable of reversible magnetic-field-induced strains (MFIS). These are generated by twin boundaries moving under the influence of an internal stress produced by a magnetic field through the magnetocrystalline anisotropy. While MFIS are very large (up to 10%) for monocrystalline Ni-Mn-Ga, they are near zero (<0.01%) in fine-grained polycrystals due to incompatibilities during twinning of neighboring grains and the resulting internal geometrical constraints. By growing the grains and/or shrinking the sample, the grain size becomes comparable to one or more characteristic sample sizes (film thickness, wire or strut diameter, ribbon width, particle diameter, etc), and the grains become surrounded by free space. This reduces the incompatibilities between neighboring grains and can favor twinning and thus increase the MFIS. This approach was validated recently with very large MFIS (0.2-8%) measured in Ni-Mn-Ga fibers and foams with bamboo grains with dimensions similar to the fiber or strut diameters and in thin plates where grain diameters are comparable to plate thickness. Here, we review processing, micro- and macrostructure, and magneto-mechanical properties of (i) Ni-Mn-Ga powders, fibers, ribbons and films with one or more small dimension, which are amenable to the growth of bamboo grains leading to large MFIS, and (ii) "constructs" from these structural elements (e.g., mats, laminates, textiles, foams and composites). Various strategies are proposed to accentuate this geometric effect which enables large MFIS in polycrystalline Ni-Mn-Ga by matching grain and sample sizes.

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Martensitic transformation in Ni2MnGa films: A ferromagnetic resonance study

Cited by 29 publications

References 25 publications

Element-specific electronic structure and magnetic properties of an epitaxialNi51.6Mn32.9Sn15.5thin film at the austenite-martensite transition

Element-specific electronic structure and magnetic properties of an epitaxialNi51.6Mn32.9Sn15.5thin film at the austenite-martensite transition

Martensitic Transformations and Magnetic Properties of Ni-Mn-Sn Heusler Alloy Films

Size Effects on Magnetic Actuation in Ni‐Mn‐Ga Shape‐Memory Alloys

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