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 → Imma → I4/mcm → Pmm. 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 ∼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,A_z). The same magnetic structure is observed in each of the four crystal structures.