FERRIMAGNETIC-ANTIFERROMAGNETIC PHASE-TRANSITION IN MN2-XCRXSB - ELECTRONIC-STRUCTURE AND ELECTRICAL AND MAGNETIC-PROPERTIES

Self-consistent spin-polarized energy-band calculations have been performed for Mn2Sb for a ferrimagnetic (FI), ferromagnetic (F), and antiferromagnetic (AF) spin alignment. The calculated local moments on the two types of Mn atoms are in agreement with values obtained from neutron diffraction for FI Mn2Sb. A comparison of the band structures of FI, F, and AF Mn2Sb shows characteristic differences in hybridization between the Mn 3d orbitals and Sb 5p orbitals. The covalent interactions between Mn(1) and Mn(2) 3d orbitals are responsible for a strong direct antiferromagnetic exchange within the triple layers Mn(2)-Mn(1)-Mn(2). The exchange between triple layers is attributed to a much weaker indirect exchange via Sb 5p states. We also carried out measurements of the magnetic properties and the electrical transport properties (resistivity, Seebeck effect, Hall effect) of single crystals and polycrystalline samples of Mn2Sb and Mn2-xCrxSb (x < 0.2). The Cr-doped samples show a phase transition from an AF to a FI state. This phase transition is associated with strong changes of the electrical transport properties. We have analyzed these changes in terms of the calculated band structures of FI and AF Mn2Sb.