Anomalous transport properties ofNi2Mn1−xCrxGaHeusler alloys at the martensite-austenite phase transition

Abstract

The martensite-austenite phase transition in a series of $\mathrm{N}{\mathrm{i}}_{2}\mathrm{M}{\mathrm{n}}_{1\ensuremath{-}x}\mathrm{C}{\mathrm{r}}_{x}\mathrm{Ga}$ Heusler alloys has been investigated by x-ray diffraction, dc magnetization, and electrical resistivity measurements. With increasing Cr concentration, the martensitic phase transformation shifts to higher temperature while the ferromagnetic transition shifts to lower temperature. For $xl0.5$, the martensitic transformation occurs in a ferromagnetic state, while for $xg0.5$, the transition occurs in a paramagnetic state. The Cr doping results in a reconstruction of the electronic structure, particularly, near the Fermi level, which is indicated in the resistivity data where a systematic jumplike anomaly is observed in the vicinity of the martensite-austenite phase transformation. With increasing Cr concentration, the magnitude of the jump in resistivity changes dramatically from less than $1%$ to nearly $18%$ The results are discussed considering the fundamental interactions in Heusler alloys.