The authors present investigations of the crystal structure the microstructure and the magnetic properties of the inter-metallic compounds XMnSb (X=Pt, Ni, Co, Au, Cu) and PtMnSn. It was found that several of these materials contain precipitates of other phases and/or large atomic disorder, which can be influenced by heat treatment. The magnetic properties show an effective paramagnetic moment which differs from the value corresponding to the saturation moment at 0 K. This effect is attributed to a decrease of the conduction electron spin polarisation at high temperature.

For pt.I see ibid., vol.1, p.2341 (1989). The electrical resistivity and the Hall effect of inter-metallic compounds XMnSb (X=Pt, Ni, Au) and PtMnSn were investigated in the temperature region 4-1000 K. The results for the anomalous Hall effect were analysed in terms of skew scattering and side-jump contributions. This analysis is possible in a half-metallic ferromagnet because the conduction electron spin polarisation at T=0 K is known.

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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 Sp 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 Sp 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 "Cr"Sb (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.

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