Influence of A-Site Cations on Structural and Magnetic Properties in the Double Perovskites Ca_2−xSr_xMnWO₆ and Sr_2−xBa_xMnWO₆ (0 ≤ x ≤ 2.0)

Abstract

We have investigated the structural and magnetic behavior of the series of double perovskites. The compounds exhibit a monoclinic to cubic structural transition as a function of composition and paramagnetic to antiferromagnetic transition as a function of temperature. The systems shows higher symmetries with the introduction of larger A-site cations. The antiferromagnetic transition temperature (T_N) decreases with the increase of the A-site ionic radius. Rietveld refinement of neutron powder diffraction (NPD) data shows that all the compounds are of B-site ordered double perovskite type. Bond valence sum (BVS) calculation shows that the Mn and W are in di- and hexavalent states, respectively, for all of the compositions investigated. The symmetry is increasing and T_N is decreasing with an increase in the tolerance factor, t.

Keywords:

• Neutron diffraction
• crystal structure
• double perovskite
• magnetic measurements

Acknowledgements

The financial support from the Royal Swedish Academy of Sciences (KVA), the Swedish Natural Science Research Council (NFR), the Swedish Foundation of Strategic Research (SSF) and Bangladesh Atomic Energy Commission (BAEC) are gratefully acknowledged.