Geometrically frustrated magnetic behavior of Sr₃NiRhO₆ and Sr₃NiPtO₆

Abstract

The results of ac and dc magnetic susceptibility (χ), isothermal magnetization and heat-capacity (C) measurements as a function of temperature (T) are reported for Sr₃NiRhO₆ and Sr₃NiPtO₆, containing magnetic chains arranged in a triangular fashion in the basal plane and crystallizing in K₄CdCl₆-derived rhombohedral structure. The results establish that both the compounds are magnetically frustrated, however, in different ways. In the case of the Rh compound, the χ data reveal that there are two magnetic transitions, one in the range 10-15 K and the other appearing as a smooth crossover near 45 K, with a large frequency dependence of ac χ in the range 10-40 K; in addition, the features in C(T) are smeared out at these temperatures. The magnetic properties are comparable to those of previously known few compounds with "partially disordered antiferromagnetic structure". On the other hand, for Sr₃NiPtO₆, there is no evidence for long-range magnetic ordering down to 1.8 K despite a large value of paramagnetic Curie temperature. In this sense, this compound may be classified as a spin liquid arising out of geometrical frustration.