The magnetic and chemical ordering of the heusler alloys Pd2MnIn, Pd2MnSn and Pd2MnSb

Abstract

The magnetic and crystallographic structures of the alloys Pd₂MnIn, Pd₂MnSn and Pd₂MnSb are described. The three alloys are shown to have the Heusler (L2₁) structure, and to exhibit magnetic order. Pd₂MnIn can be obtained in ordered and partially disordered forms by suitable heat treatment. The ordered alloy is anti-ferromagnetic with a Néel temperature of 142°K. The magnetic structure has been determined from neutron diffraction measurements. The magnetic moments of 4·3 μB are confined to the Mn atoms, which are aligned in ferromagnetic (111) planes, with neighbouring planes oriented antiparallel as in NiO. In the partially disordered alloy most of the former anti-ferromagnetic order is destroyed along with the chemical order, but is replaced by anti-ferromagnetic order on a magnetic unit cell half the original size. The structures of Pd₂MnSn and Pd₂MnSb are insensitive to heat treatment. Both alloys are ordered, and ferromagnetic, with the magnetic moments residing on the Mn atoms. The Pd₂MnSn has a Curie point at 189°K and a magnetic moment of 4·23 μB. Pd₂MnSb has a Curie point at 247°K, and a magnetic moment of 4·40 μR.