Fundamental Aspects of Magnetic Shape Memory Alloys: Insights from &lt;i&gt;Ab Initio&lt;/i&gt; and Monte Carlo Studies

Peter Entel,Sanjeev K Nayak,Mario Siewert,Antje Dannenberg,Vasiliy D Buchelnikov,Markus E Gruner,Heike C Herper

doi:10.4028/www.scientific.net/msf.635.3

Fundamental Aspects of Magnetic Shape Memory Alloys: Insights from <i>Ab Initio</i> and Monte Carlo Studies

Peter Entel, Sanjeev K Nayak + Show 5 more

Open Access

https://doi.org/10.4028/www.scientific.net/msf.635.3

Copy DOI

Abstract

Ferromagnetic Heusler alloys like Ni-Mn-Z (Z = Al, Ga, In, Sn, Sb), which undergo a martensitic phase transformation, are on the edge of being used in technological applications involving actuator and magnetocaloric devices. The other class of ferromagnetic full Heusler alloys like Co-Mn-Z (Z = Al, Si, Ga, Ge, Sn) not undergoing a structural phase transition, are half-metals (in contrast to the Ni-based systems) with high spin polarization at the Fermi level and are of potential importance for future spintronics devices. On the basis of recent ab initio calculations, we highlight the main differences between the two classes of Heusler based materials.

Highlights

Since the pioneering work of Webster et al [1, 2], there has been new interest in a particular class of ferromagnetic (FM) shape memory alloys (MSMA), which undergo a structural transformation from the FM high-temperature cubic L21 phase to the tetragonally distorted 5M or 7M phase, which shows an extremely large strain of up to 10% in an external field of less than 1 Tesla [3,4,5,6]
What remains to be done from a practical point of view regarding the use of MSMA and magneto-caloric (MCE) devices is to find new FM Heusler alloys which allow higher working temperatures
From a theoretical point of view the realization of half-metallic Heusler alloys, with a 100% spin polarization at the Fermi level depends on details of the electronic structure and the valence electron number per atom, e/a, limiting the possible candidates, for instance, see Galanakis et al [12, 13]

Summary

Introduction

Since the pioneering work of Webster et al [1, 2], there has been new interest in a particular class of ferromagnetic (FM) shape memory alloys (MSMA), which undergo a structural transformation from the FM high-temperature cubic L21 phase to the tetragonally distorted 5M or 7M phase, which shows an extremely large strain of up to 10% in an external field of less than 1 Tesla [3,4,5,6].

Results

Conclusion