Abstract
A study of the crystallographic and magnetic structures of the oxides Sr~2~MReO~6~ (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 __I__4/m, and contains an almost completely ordered array of the tilted MO~6~ and ReO~6~ octahedra. When the temperature is decreased, Sr~2~CoReO~6~ and Sr~2~ZnReO~6~ undergo a phase transition to a monoclinic symmetry (__P__2~1~/n space group). The low‐temperature magnetic structures, which were determined by NPD, show antiferromagnetic behavior for Sr~2~NiReO~6~ and Sr~2~CoReO~6~. For Sr~2~NiReO~6~, a antiferromagnetic structure was observed below T~N~ = 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) μ~B~ for the Ni^2+^ ions. Sr~2~CoReO~6~ is an antiferromagnet below T~N~ = 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) μ~B~ is refined for the Co^2+^ cations at 2 K. For Sr~2~ZnReO~6~, the magnetic measurements suggest the existence of an ordered magnetic array of Re^6+^ (5d^1^) spins, which cannot be observed by NPD data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)