Doping effect on the martensitic and magnetic phase transitions of Heusler-type Ni<inf>2</inf>MnGa

Abstract

While Heusler-type Ni 2 MnGa exhibits both ferromagnetic and martensitic phase transitions at 380 K and 220 K, respectively, Ni 2 MnAl with the L2 1 structure shows only a ferromagnetic ordering near room temperatures. In this work, we alloyed both compounds with different Al/Ga ratio to study the interplay between martensitic and magnetic phase transitions of Ni 2 MnGa 1−x Al x . Results indicate that both martensitic and magnetic transition temperatures considerably increase for the low Al concentration (x 0.10), a drastic suppression of martensitic transition along with a linear decrease of magnetic ordering temperature takes place. Such observations are in contrast to the general expectation for the nonmagnetic doping. It thus points out that the effect of disorder introduced by the Al substitution should play an important role on the phase transition characteristics of these alloys.