Magnetic structures of Mn3-xFexSn2: an experimental and theoretical study

TL;DR

This study combines neutron diffraction experiments and electronic structure calculations to analyze the magnetic structures of Mn3-xFexSn2 alloys, revealing complex magnetic phases and the influence of band mechanisms on canting.

Contribution

It provides new insights into the magnetic configurations of Mn3-xFexSn2, including the stabilization of canted ferromagnetic states by band mechanisms and symmetry distortions.

Findings

Four magnetic structures identified as temperature and composition vary.

Electronic calculations agree with experimental magnetic moments and canting angles.

Weak monoclinic distortion at low temperature influences magnetic structure stabilization.

Abstract

We investigate the magnetic structure of Mn3-xFexSn2 using neutron powder diffraction experiments and electronic structure calculations. These alloys crystallize in the orthorhombic Ni3Sn2 type of structure (Pnma) and comprise two inequivalent sites for the transition metal atoms (4c and 8d) and two Sn sites (4c and 4c). The neutron data show that the substituting Fe atoms predominantly occupy the 4c transition metal site and carry a lower magnetic moment than Mn atoms. Four kinds of magnetic structures are encountered as a function of temperature and composition: two simple ferromagnetic structures (with the magnetic moments pointing along the b or c axis) and two canted ferromagnetic arrangements (with the ferromagnetic component pointing along the b or c axis). Electronic structure calculations results agree well with the low-temperature experimental magnetic moments and canting angles throughout the series. Comparisons between collinear and non-collinear computations show that the canted state is stabilized by a band mechanism through the opening of a hybridization gap. Synchrotron powder diffraction experiments on Mn3Sn2 reveal a weak monoclinic distortion at low temperature (90.08 deg at 175 K). This lowering of symmetry could explain the stabilization of the c-axis canted ferromagnetic structure, which mixes two orthorhombic magnetic space groups, a circumstance that would otherwise require unusually large high-order terms in the spin Hamiltonian.