Study of the antiferromagnetism of Mn5Si3: an inverse magnetocaloric effect material

Abstract

The intermetallic compound Mn5Si3 has been studied by high-resolution Time-of-Flight (TOF) neutron powder diffraction. At room temperature, Mn5Si3 is paramagnetic and it crystallizes in the P63/mcm hexagonal space group. Magnetic susceptibility and specific heat measurements show clearly two major anomalies. At 100(1) K, a transition (Tm1) corresponds to a collinear antiferromagnetic ordering (AF1). The second transition at 62(1) K (Tm2), which was still unclear, highlights a magneto-structural distortion from an orthorhombic symmetry (AF1) to a monoclinic symmetry (AF2), which could be influenced by a low magnetic field. Such a magneto-structural change is directly associated with the inverse magnetocaloric effect behaviour of this material. A new description by means of the commensurate magnetic superspace groups, Ccmm1′(0β0)00ss and C21/m1′(αβ0)0ss, has been used to refine properly the low temperature antiferromagnetic structures. Band structure calculations using the self-consistent, spin-polarized TB-LMTO method were accomplished to support the magnetic properties observed at low temperature.