Crystal and Magnetic Structure of Sr2MReO6 (M = Ni, Co, Zn) Double Perovskites: A Neutron Diffraction Study

Abstract

AbstractA study of the crystallographic and magnetic structures of the oxides Sr2MReO6 (M = Ni, Co, Zn) was carried out on polycrystalline samples by using neutron powder diffraction (NPD) data. At room temperature the perovskite crystal structure is tetragonal, space group I4/m, and contains an almost completely ordered array of the tilted MO6 and ReO6 octahedra. When the temperature is decreased, Sr2CoReO6 and Sr2ZnReO6 undergo a phase transition to a monoclinic symmetry (P21/n space group). The low‐temperature magnetic structures, which were determined by NPD, show antiferromagnetic behavior for Sr2NiReO6 and Sr2CoReO6. For Sr2NiReO6, a antiferromagnetic structure was observed below TN = 30 K, which was characterized by a propagation vector of k = (1/2, 0, 1/2); this structure remains stable down to 2 K and shows an ordered magnetic moment of 1.3(5) μB for the Ni2+ ions. Sr2CoReO6 is an antiferromagnet below TN = 60 K and down to 2 K; the magnetic structure is defined by a propagation vector k = (0, 0, 1/2) and an ordered magnetic moment of 2.75(7) μB is refined for the Co2+ cations at 2 K. For Sr2ZnReO6, the magnetic measurements suggest the existence of an ordered magnetic array of Re6+ (5d1) spins, which cannot be observed by NPD data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)