Structural phase transitions and magnetic order in SrTcO3

Abstract

The structure of the perovskite SrTcO3 has been investigated using both synchrotron X-ray and neutron powder diffraction. At room temperature SrTcO3 is orthorhombic as a consequence of cooperative tilting of the corner sharing TcO6 octahedra. The tilts are sequentially removed as the sample is heated with the oxide displaying the sequence of structres Pnma [rightward arrow] Imma [rightward arrow] I4/mcm [rightward arrow] Pm3[3 with combining macron]m. Neutron powder diffraction data collected in the temperature range 4-1023 K indicate that SrTcO3 has G-type antiferromagnetic structure, in which each Tc moment is antiparallel to its six nearest neighbours, below [similar]1000 K. The magnetic structure is collinear antiferromagnetic with the technetium moments parallel to c-axis and can be described by the propagation vector k = [0,0,0] and the basis vector (0,0,Az). The same magnetic structure is observed in each of the four crystal structures.© 2011, Royal Society of Chemistry