Magnetic Properties and Exchange Bias Behavior in Nanocrystalline (Ho1-xSmx)2CoMnO6 (x = 0 – 0.5) Double Perovskite

Abstract

Single phase nanocrystalline samples of double perovskite (Ho1-xSmx)2CoMnO6 (x = 0 – 0.5) (HSCMO) were prepared by gel combustion method and their crystal structure and magnetic properties are studied. These samples crystallize into monoclinic structure with P21/n space group and their lattice parameters increase with Sm concentration. Temperature variation of magnetization measurements show that all the prepared samples exhibit ferromagnetic (FM) transition with transition temperature (TC) increasing from 83 K for x = 0.0 to 115 K for x = 0.5. A secondary rise in magnetization is observed for T < 50 K and is attributed to FM interaction between rare-earth (RE) and transition metal (TM) ions. The FM transition at higher temperature is attributed to strong super-exchange interaction in Co2+-O - Mn4+ networks. The M−H loops recorded at 5 K show a saturation magnetization (MS) in the range of 11.64 µB/f.u. for x = 0.0 to 7.86 µB/f.u. for x = 0.5 and it clearly indicates the contribution of RE ions to the net ferromagnetic moment. All the prepared samples show exchange bias behaviour with exchange bias field up to 237 Oe at 5 K and is attributed to competition between FM moment of TM ions and the spin canted magnetic moment of RE ions.