SEMICONDUCTOR-METAL TRANSITION AND THE ONSET OF ITINERANT FERROMAGNETISM IN THE HEUSLER PHASES TICOSN-TICOSB

The magnetic and transport properties of the TiCoSnxSb1-x solid soluti ons with the cubic MgAgAs structure have been studied, and show the on set of ferromagnetism associated with a semiconductor to metal transit ion, keeping the same 3d elements and varying the number of s-p electr ons. The transition from TiCoSn ferromagnetic metal to the non-magneti c semiconductor TiCoSb occurs through an intermediate metallic Pauli-l ike state. The variations of the Curie temperature as a function of sa turation and effective paramagnetic moments are related to the itinera nt ferromagnetism model. A comparison is made with the TiCoxNi1-xSn se ries, where the transition occurs directly from ferromagnetic metal to semiconducting state.