Magnetoelastic coupling and field-induced metamagnetism in the cubic Heusler alloy Mn sub(1.7)Fe sub(1.3)Si

Abstract

We present a systematic study of the structural, magnetic, and transport properties of the cubic Heusler alloy Mn sub(1.7)Fe sub(1.3)Si. Room-temperature x-ray diffraction and temperature-dependent neutron powder diffraction confirm long-range cubic L2 sub(1) ordering, with no crystallographic phase transition down to 20 K. Magnetization measurements reveal a paramagnetic-ferromagnetic/ferrimagnetic transition at T sub(c) = 85 K, followed by a spin-reorientation transition between 65 K and 55 K. Neutron diffraction shows that long-range antiferromagnetic (AFM) order develops only below 55 K, stabilizing a canted AFM ground state. Anomalies in the temperature dependence of the unit-cell volume across magnetic transitions provide clear evidence of magnetoelastic coupling. Electrical resistivity measurements confirm metallic behaviour. At low temperatures, magnetization and magnetotransport data reveal a field-induced metamagnetic transition accompanied by irreversibility, metastability, and magnetic phase coexistence, leading to a low-field coexistence region in the H-T phase diagram below 2.5 T. Notably, the metamagnetic transition is purely magnetic and occurs without any structural transformation. These results clarify the complex magnetic behaviour of Mn sub(1.7)Fe sub(1.3)Si and highlight the role of spin-lattice coupling in Mn-based Heusler alloys.