Synthesis, structures and magnetic properties of n=3 Ruddlesden–Popper compounds Ca4Mn3−xTaxO10 (0≤x≤0.3)

The structural and magnetic properties of Ta-doped Ca4Mn3−xTaxO10 (0≤x≤0.3) compounds have been investigated. Structural refinement indicates that the Ta doping maintains the orthorhombic layered perovskite structure with space group Pbca as Ca4Mn3O10 but induces an increase in both unit cell volume and octahedral distortion. The magnetization measurements reveal that the magnetization first increases and reaches to maximum for the x=0.1 sample and then gradually decreases with the increase of Ta content. There appear short-range ferromagnetic (FM) clusters in all the doped samples, which are caused by the double-exchange interaction between Mn4+ and Mn3+ that is induced by the charge compensation effect. As x is higher than 0.1, the overall results show evidence for the gradual appearance of a cluster glass behavior. When x increases to 0.3, the long-range antiferromagnetic (AFM) ground state is melted into the short-range magnetically ordered regions due to the increase of Ta5+ and Mn3+ at the expense of Mn4+. The competition between AFM regions and FM clusters makes the short-range magnetic components frustrate when the temperature falls to a frustrating point, and thus cluster glass transition occurs.