Ni-Mn-Ga films in the austenite and the martensite structures at room temperature: Uniaxial texturation and epitaxial growth

TL;DR

This paper reports the fabrication and analysis of Ni-Mn-Ga films in austenite and martensite phases at room temperature, focusing on their texture and epitaxial growth using sputtering techniques.

Contribution

It introduces methods for producing both polycrystalline and epitaxial Ni-Mn-Ga films with controlled textures and phases at room temperature.

Findings

Polycrystalline films exhibit strong (022) fiber texture.

Epitaxial films crystallize in both austenite and martensite phases.

Epitaxial growth achieved on MgO substrates at various temperatures.

Abstract

Ni-Mn-Ga films in the austenite and the martensite structures at room temperature have been obtained using the DC magnetron sputtering technique. Two elaboration processes were studied. A first batch of samples was deposited using a resist sacrificial layer in order to release the film from the substrate before vacuum annealing. This process leads to polycrystalline films with a strong (022) fiber texture. The martensitic phase transformation of such polycrystalline freestanding films has been studied by optical and scanning electron microscopy. A second batch of samples was grown epitaxially on (100)MgO substrates using different deposition temperatures. The texture has been analyzed with four-circle X-ray diffraction. Epitaxial films crystallized both in the austenite and the martensite structures at room temperature have been studied.