Magnetic Properties of the Ordered Double Perovskite Sr2MnTeO6

Abstract

AbstractThe ordered double perovskite Sr2MnTeO6 was prepared by the freeze‐drying method. The nuclear and magnetic structures were determined by both X‐ray and neutron (D2B and D1B) powder diffraction. A distorted, double perovskite structure type described by the monoclinic P121/n1 space group is observed at room temperature and down to 4 K. The room temperature EPR spectrum shows an isotropic signal centered at a g value of 1.998 indicating that manganese ions are in the +2 oxidation state. At low temperature the EPR signal broadens as the exchange and dipolar interactions between Mn2+ cations increase. Below 25 K no signal is observed, indicating that the sample is magnetically ordered. The dc magnetic susceptibility shows the existence of antiferromagnetic interactions with an ordering temperature around 20 K. A sharp λ‐type anomaly observed at 19 K in the specific heat curve and refinement of low‐temperature neutron diffraction data confirm the presence of a three‐dimensional, antiferromagnetic ordered structure with an ordering temperature of ca. 23 K. The propagation vector of the magnetic structure is k = [0,0,0], yielding a type I antiferromagnetic ordering between Mn2+ (S = 5/2) cations. At 2 K, each manganese ion is antiferromagnetically aligned to 8 out of 12 nearest‐neighbors at an approximate distance of 5.6 Å. This magnetic structure can be viewed as being composed of ferromagnetic arrangement of Mn2+ moments in the ab plane, coupled antiferromagnetically along the c axis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)