Martensite structures and twinning in substrate-constrained epitaxial Ni-Mn-Ga films deposited by a magnetron co-sputtering process

TL;DR

This study demonstrates that co-sputtering enables precise composition control and epitaxial growth of Ni-Mn-Ga films, facilitating the tuning of martensite structures and twinning for magnetic shape memory applications.

Contribution

It introduces a co-sputtering method for fabricating Ni-Mn-Ga epitaxial films with controlled martensite content and twinning structures.

Findings

Co-sputtering allows precise composition control.

Epitaxial growth of austenite is maintained at high temperature.

Martensite content and twinning can be tuned at room temperature.

Abstract

In order to obtain Ni-Mn-Ga epitaxial films crystallized in martensite structures showing Magnetic-Induced Rearrangement (MIR) of martensite variants, a fine control of the composition is required. Here we present how the co-sputtering process might be helpful in the development of Ni-Mn-Ga epitaxial films. A batch of epitaxial Ni-Mn-Ga films deposited by co-sputtering of a Ni-Mn-Ga ternary target and a pure manganese target has been studied. The co-sputtering process allows a precise control of the film compositions and enables keeping the epitaxial growth of Ni-Mn-Ga austenite during deposition at high temperature. It gives rise to tune the content of the MIR-active 14-modulated martensite in the film at room temperature, as well as micro and macro-twinned domains sizes.