Magnetic Structure and the Hall Resistivity of Cu_1-xZn _xCr₂Se₄

Neutron diffraction, NMR and other magnetic and transport studies have been carried out on several samples of the ferromagnetic Cu_1-xZn _xCr₂Se₄ to extract information on the relationship between the unusual behavior of the Hall resistivity ρ _/H and the non-trivial magnetic structure or the spin chiral order. For x = 0.3, 0.5 and 0.7, conical structures have been adopted to explain the observed data of neutron diffraction, and parameters which describe the structures have been determined. Arguments on the differences among the values of the Cr moments observed by various method are presented, which elucidates the characteristics of the magnetic state of the present system. It is confirmed that along with the gradual growth of the conical structure, the anomalous Hall coefficient R_s changes its sign. The correlation between the conical angle 0 and the low temperature value of |R_s| is pointed out.