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Abstract: We report the observation of room temperature magnetism and ferroelectricity in polycrystalline BaTi0.95−x Hf0.05Co x O3 ceramics, where x=0.05, 0.1, and 0.15. Magnetic and ferroelectric hysteresis loops are strongly influenced by Co ion doping concentration. Magnetization of doped compositions is enhanced with increasing of Co ion concentration. Room temperature ferromagnetism is also observed in BaTi0.8Hf0.05Co0.15O3. Simultaneously, the saturation electric polarization value is decreased with the increasing of Co ion doping concentration. Our XPS results have revealed the presence of oxygen vacancies in doped samples. Oxygen vacancies have significant influence on magnetic and ferroelectric properties of doped BaTiO3. Observation of room temperature magnetism in our samples may be due to the exchange interactions of cobalt ions through oxygen vacancies. [Copyright &y& Elsevier]

Abstract: Cobalt (Co) doped HoMnO3 (HMO) bulk ceramics having structural formula HoMn1−x Co x O3 (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 10K 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 530K 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. [Copyright &y& Elsevier]

Abstract: Our paper reports structural, magnetic and ferroelectric properties of Ni doped barium titanate. Ceramics samples of BaTi1−x Ni x O3 (here, x=0, 0.05, 0.1, and 0.15) were prepared through solid state sintering technique. It is revealed from structural studies that the phase transformation from tetragonal to hexagonal phase is strongly influenced by Ni doping concentration. Magnetism is induced in doped composition and the value of magnetism is dependent upon Ni ion concentration. This enhanced magnetic effect is likely to originate from carrier-mediated exchange interactions. Ferroelectricity was observed in all samples at room temperature, but it was decreased by Ni doping. [Copyright &y& Elsevier]