Structural and magnetic properties of single-crystalline spinel systems ZnCr 2− x In xSe 4

Abstract

The single crystals of In 3+-doped zinc chromium selenide spinel ZnCr 2Se 4 were prepared by a chemical transport method and characterized by X-ray diffraction, magnetic measurements and ESR spectroscopy in order to examine an effect of nonmagnetic indium on the structural and magnetic properties of the system. The X-ray diffraction analysis has shown that only small amount of In entered the octahedral sites in the cubic spinel structure with space group F d 3 ¯ m . As compared with parent ZnCr 2Se 4, the unit cell dimensions increased slightly with increasing In content, however at the In concentration of about 10%, the structures exhibited a certain amount of octahedral vacancies. For examined compounds the Neel temperature is very similar to that of the parent spinel ZnCr 2Se 4, whereas the paramagnetic Curie temperature is much lower (of about 59 K) than that for matrix. It means that the frustration introduced into systems by B-sublattice indium dilution reflects the change of ferromagnetic interactions in the magnetic exchange. The temperature dependence of the ESR linewidth over region ( T/ T N)>8 is interpreted by an occurrence of spin–phonon interaction. The interesting feature of the low-field magnetization is that the magnetic irreversibility observed in the separation of the FC and ZFC curves below T N is consistent with a new, weak resonance-like features.