Structural and magnetic studies of the ruthenium perovskites Ba2-xSrxHoRuO6

Abstract

The series of ruthenate double perovskites Ba2-xSrxHoRuO6 (0 ≤ x ≤ 2) have been synthesized using solid state methods. The crystal structures of the series have been determined by high resolution synchrotron X-ray diffraction and show the sequence of structures to be Fm3̅m (a0a0a0) (0 ≤ x ≤ 0.6) → I4/m (a0a0c-) (x = 0.8) → I2/m (a0b-b-) (1.0 ≤ x ≤ 1.2) → P21/n (a-a-c+) (1.4 ≤ x ≤ 2.0). A similar progression of structures is observed in the sample BaSrHoRuO6 with increasing temperature. Magnetic characterisation of these materials was undertaken utilising variable temperature bulk magnetic susceptibility, isothermal magnetisation and low temperature neutron powder diffraction measurements. All members of the series order antiferromagnetically with the Ru and Ho sublattices ordering at different temperatures between 50 and 16 K. The presence of the magnetic Ho3+ at the perovskite B site stabilises the antiferromagnetic (AFM) ordering of the Ru sublattice. The addition of Sr for Ba beyond x = 1.2 weakens the AFM superexchange interactions through induced structural distortions, resulting in a canted AFM ground state.