Dopant mediated multiferroic behavior of HoMn1−xCoxO3 (x=0, 0.025, 0.05, 0.1)

Cobalt (Co) doped HoMnO3 (HMO) bulk ceramics having structural formula HoMn1−xCoxO3 (x=0, 0.025, 0.05, 0.1) are prepared using a conventional solid state reaction route and the effect of Co substitution at Mn site for the improvement of its structural, dielectric and multiferroic properties is studied. Optimizing the dopant concentration of Co (x=0.1), hexagonal phase (P63cm) of HMO is completely transformed to orthorhombic (Pbnm) structure. From magnetic measurement, it is observed that incorporation of Co atoms into HMO shows low temperature ferromagnetic behavior around 10 K and its origin is attributed to the double exchange interaction between Mn3+- and Mn4+ ions. The materials also exhibit a sharp dielectric anomaly well above the room temperature around 530 K at the concentration of x=0.1. Shifting of both magnetic transition as well as dielectric anomaly curve towards higher temperature is a clear indication for the existence of strong correlation between magnetic and electric dipole ordering. From XPS spectrum, it is found that oxidation state of Co atoms is +2 state and Mn atoms are both in +3 and +4 mixed state.