From nonmagnetic semiconductor to itinerant ferromagnet in the TiNiSn-TiCoSn series

The magnetic properties and resistivity of the cubic solid solutions TiCo x Ni − x Sn, where a metal-to-semiconductor transition occurs, have been studied. The effective moment of Co does not change much from TiCoSn (itinerant ferromagnet) to Co diluted in TiNiSn, whereas the ferromagnetic interactions drop rapidly due to the lowering of the density of states at the Fermi level. A comparison is done with the metallic solid solutions TiCo x Ni 2− x Sn and TiCo x Sn, which also exhibit itinerant ferromagnetism, but with a different behaviour of cobalt effective moments and interactions as function of composition. The resistivity and magnetoresistance show a strong influence of spin fluctuations for concentrations close to the magnetic-nonmagnetic borderline.