Nonlinear Temperature Variation Research Articles

Magnetic Properties of the Systems HgCr2S4–CdCr2S4 and ZnCr2Se4–CdCr2Se4

The distribution of magnetic ions and the crystallographic parameters remain essentially constant throughout the system Hg1−xCdxCr2S4. A study of the magnetic properties of this system was therefore undertaken in order to further elucidate the origin of the large difference in the magnetic properties already reported on the endpoints. The Curie temperature was found to increase nonlinearly from 36.0° to 84.5°K as x varies from 0 to 1. The low-temperature F-AF (ferromagnetic-antiferromagnetic) transition and metamagnetism of HgCr2S4 penetrate well into the system, up to x≃0.37 at which the F-AF transition temperature approaches 0°K. The distribution of magnetic ions remains constant, but the crystallographic parameters vary in the system Zn1−xCdxCr2Se4. Nevertheless, since ZnCr2Se4 is an antiferromagnetic with large positive θ, while CdCr2Se4 is a ferromagnet, a magnetic study of this system provides further evaluation of the theory of the ferromagnetic spinels. In addition, the evaluation of the nonlinear variation of ferromagnetic Curie temperature from 22° to 129.5°K, observed for x=0.35 to 1, permits qualitative evaluation of the exchange parameters of ZnCr2Se4. The Néel temperatures were found to be ≃20°K for the whole antiferromagnetic region of the system x=0 to 0.35. F-AF transitions in zero field and/or metamagnetism are also observed over a large compositional region.