Structural and Magnetic Properties of Epitaxial Ni&lt;sub&gt;2&lt;/sub&gt;MnGa Thin Films

Eichhorn, Tolga; Jakob, G.

doi:10.4028/www.scientific.net/msf.635.155

Cited by 11 publications

(1 citation statement)

References 11 publications

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“…[25][26][27][28][29][30] Moreover, fabrication of polycrystalline shape-memory films with a substrate is of great interest among researchers. Previously, a few studies have reported on Ni-Mn-Ga thin films grown on various substrates such as Al 2 O 3 , 31 NaCl, 32 MgO, 33 and Si.…”

Section: Introductionmentioning

confidence: 99%

Structural and Magnetic Properties of Sputter-Deposited Polycrystalline Ni-Mn-Ga Ferromagnetic Shape-Memory Thin Films

Kumar

Seenithurai

Raja

et al. 2015

Journal of Elec Materi

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Polycrystalline Ni-Mn-Ga ferromagnetic shape-memory thin films have been deposited on Si (100) substrates using a direct-current magnetron sputtering technique. The microstructure and the temperature dependence of magnetic properties of the films have been investigated by x-ray diffraction, scanning electron microscopy, and thermomagnetic measurements. As-deposited Ni 50.2 Mn 30.6 Ga 19.2 film showed quasi-amorphous structure with paramagnetic nature at room temperature. When annealed at 873 K, the quasi-amorphous film attained crystallinity and possessed L2 1 cubic ordering with high magnetic transition temperature. Saturation magnetization and coercivity values for the annealed film were found to be 220 emu/cm 3 and 70 Oe, respectively, indicating soft ferromagnetic character with low magnetocrystalline anisotropy. The magnetic transitions of the film deposited at 100 W were above room temperature, making this a potential candidate for use in microelectromechanical system devices.

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Section: Introductionmentioning

confidence: 99%

Structural and Magnetic Properties of Sputter-Deposited Polycrystalline Ni-Mn-Ga Ferromagnetic Shape-Memory Thin Films

Kumar

Seenithurai

Raja

et al. 2015

Journal of Elec Materi

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Structure and Microscopic Magnetism of Epitaxial Ni–Mn–Ga Films

et al. 2012

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We report on the structural and magnetic properties of epitaxial thin films of the ferromagnetic shape memory material Ni–Mn–Ga prepared by DC magnetron sputter deposition. Different substrate materials, i.e., MgO(100) and Al2O3(11−20) allow for a tailored epitaxial growth. Using a sacrificial chromium buffer layer freestanding epitaxial films are obtained. In combination with photolithography partially freestanding structures such as microbridges are fabricated. The complex martensite crystal structure in substrate‐constrained and freestanding films is studied by means of X‐ray diffraction. The identified asymmetric twin variant configuration is associated with a macroscopic surface pattern observed by optical microscopy. The absence of magnetic‐field induced strain in the (100) oriented samples is explained on basis of the detected twin variant configuration using a simplified model. Taking advantage of the thin film geometry spectroscopic methods are applied to the samples. The measurements provide the first experimental test for changes in the electronic structure of the involved 3d metals during a martensitic transition. Exploiting the X‐ray magnetic circular dichroism quantitative information on the element‐specific spin and orbital magnetic moments are accessed. In addition, angular‐dependent experiments allow us to trace the microscopic origin of the magnetic anisotropy in Ni2MnGa improving the fundamental understanding of this material.

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Epitaxial NiMnGa Films for Magnetic Shape Memory Alloy Microactuators

et al. 2012

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Active materials such as piezoelectrics are established in the field of microsystems application despite their low achievable strains which often require the integration of additional gear mechanisms. The ongoing search for new active materials has focused on magnetic shape memory (MSM) alloys such as NiMnGa since they combine macroscopic strains of up to 10% with a cycling frequency well above the frequencies of conventional thermal shape memory alloys. The present review focuses on preparation and analysis of NiMnGa films that can eventually be integrated in microsystems. Single crystal like films are prepared by epitaxial growth on suitable substrate materials. Since the magnetically induced reorientation of variants is blocked by a rigid substrate, we present different methods for releasing films from the substrates. We show that the sacrificial layer technology is the most promising approach. Further processing of the freestanding film requires a microtechnology which is adjusted to the film laminate structure. The properties of the freestanding films are compared with films on a rigid substrate. Although we observe stress‐induced twin boundary motion, the twinning stress is too high to be overcome by an external magnetic field. Therefore, it is necessary to develop suitable training methods to reduce the twinning stress below 2 MPa to enable the activation of the material by means of an external magnetic field.

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Structural and Magnetic Properties of Epitaxial Ni<sub>2</sub>MnGa Thin Films

Cited by 11 publications

References 11 publications

Structural and Magnetic Properties of Sputter-Deposited Polycrystalline Ni-Mn-Ga Ferromagnetic Shape-Memory Thin Films

Structural and Magnetic Properties of Sputter-Deposited Polycrystalline Ni-Mn-Ga Ferromagnetic Shape-Memory Thin Films

Structure and Microscopic Magnetism of Epitaxial Ni–Mn–Ga Films

Epitaxial NiMnGa Films for Magnetic Shape Memory Alloy Microactuators

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