Crystal and magnetic structure of antiferromagnetic Mn2PtPd

Abstract

We have investigated the crystal and magnetic structure of Mn2PtPd alloy using powder x-ray and neutron diffraction experiments. This compound is believed to belong to the Heusler family having crystal symmetry I4/mmm (TiAl3-type). However, in this work we found that the Pd and Pt atoms are disordered and thus Mn2PtPd crystallizes in the L10 structure having P4/mmm symmetry (CuAu-I type) like MnPt and MnPd binary alloys. The lattice constants are a = 2.86 Å and c = 3.62 Å at room temperature. Mn2PtPd has a collinear antiferromagnetic spin structure below the Néel temperature TN = 866 K, where Mn moments of ∼4 B lie in the ab-plane. We observed a strong change in the lattice parameters near TN. The sample exhibits metallic behaviour, where electrical resistivity and carrier concentration are of the order of 10-5 cm and 1021 cm-3, respectively.