Nonequilibrium phase transformation and magnetic properties of Ni3Sn2 during mechanical milling

Abstract

A nonequilibrium phase transformation in stoichiometric Ni3Sn2 during mechanical impact in a high-energy ball mill was monitored by the measurements of high-field magnetization, ac susceptibility, and x-ray diffraction. X-ray diffraction showed that the material transformed from the low-temperature Ni3Sn2 phase with Ni3Sn2-type orthorhombic structure to the high-temperature Ni3Sn2 phase with partially filled-up B8-type structure after 40 h of milling. Quenching was used to confirm the phase transformation during ball milling. The magnetization of the ball-milled high-temperature phase (metastable) is much higher than that of the quenched high-temperature phase, where both ball-milled and quenched high-temperature phases have higher magnetization than the low-temperature phase. The Curie temperature of our metastable high-temperature phase is quite close to that of the equilibrium phases (high- and low-temperature phases). The result is discussed in terms of atomic disordering induced by mechanical milling.