Magnetic Properties of the System CuCr₂Se_4-xY_x(Y=Cl, Br)

Abstract

Magnetization measurements were made on the mixed anion system CuCr 2 Se 4- x Y x ( Y =Cl, Br), in order to investigate the concentration dependence of the Curie constant and the exchange stiffness constant D as obtained from the magnetization measurements at low temperatures. From the former experiment, it is shown that the electronic state is closer to the Lotgering model rather than the Goodenough one, which is consistent with the result of our polarized neutron experiment. However, even the Lotgering model does not give satisfactory agreement with experiment unless we take account of the metallic character of the substances. Furthermore, from the latter one, it is shown that the hole-carrier responsible for the metallic conduction contributes mainly to the ferromagnetic coupling between the magnetic moments on the second-neighbour Cr atoms. The mechanism of the ferromagnetism is discussed on the basis of the above electronic state.