Anisotropy of the electrical transport properties in a Ni2MnGa single crystal: Experiment and theory

Abstract

Electrical transport properties in ferromagnetic shape memory Ni-Mn-Ga single crystal have been investigated both in experiment and theory by analyzing electrical resistivity along different crystallographic directions during heating. The experimental results show a clear first-order martensitic transformation and a large anisotropic resistivity ͑AR͒ of 23.7% at the tetragonal martensitic phase. The theoretical conductivity ͑ =1/ ͒, estimated using first-principles calculations combined with classical Boltzman transport theory, proves essential crystallographic anisotropic resistivity ͑AR= 31%͒ in the martensitic phase and agrees well with experimental results. The AR in the martensitic phase is reveled to mainly originate from the splitting of the minority-spin Ni 3d and Ga 4p states near the Fermi level and hence reconstruction of the minority-spin Fermi surface upon martensitic transformation.

Effect of Twinning on Angle-Resolved Photoemission Spectroscopy Analysis of Ni49.7Mn29.1Ga21.2(100) Heusler Alloy

“…In addition to the band splitting due to the twinned microstructure, the comparison of the ECC of austenite and martensite in Figure 1 shows a surprising fact: that the martensitic phase exhibits weak or no electron emission in its central part, i.e., there is no photoelectron signal around the Γ point, in contrast to the austenitic cubic phase. Moreover, theoretical 3D calculations of martensite also predict the photoelectron emission close to the Γ point [17,18].…”

Magnetic Shape Memory Microactuators

“…As a consequence, hysteresis-free resistance-magnetostrain relations are obtained. This indicates that the anisotropy of the electrical resistivity along the different crystallographic directions can be neglected [60,61]. Another experiment demonstrated that the inductance of a pick-up coil at the MSMA actuator may also be used for position sensing with good accuracy [62].…”