Magnetic, magnetocaloric, and dielectric properties of polycrystalline perovskite La0.7Ca0.2Pb0.1CoO3

Abstract

The polycrystalline perovskite La0.7Ca0.2Pb0.1CoO3 has been prepared by the conventional solid-state reaction technique, and then the structural, magnetic, magnetocaloric, and dielectric properties of the sample have been investigated. The monoclinic structure with space group I2/a of the sample is confirmed by X-ray diffraction investigation at room temperature. The microstructure was examined by scanning electron microscopy (SEM), and chemical composition was determined using an energy dispersive X-ray diffractometer attached to the SEM. Magnetic measurement reveals that the sample undergoes ferromagnetic to paramagnetic transition with increasing temperature and behaves as a soft magnetic material. Field cooled and zero-field cooled dc magnetization curves at low field and low temperature show divergence, indicating the coexistence of antiferromagnetic and ferro-magnetic clusters in the sample. Magnetic inhomogeneity of the sample has also been clearly confirmed by the divergence between the Curie temperature, Tc, and the paramagnetic Curie temperature, θ. The sample also shows a magnetocaloric effect at a very low field (H = 0.01 T). The high negative value of the real part of complex permittivity, ε′, reveals metallic behavior of the sample at low frequency around room temperature. However, the frequency dependent ac conductivity (σ) exhibits three distinct bands, namely, the metallic, insulating, and anomalous band, around room temperature. Temperature dependent ε′ reveals that the sample undergoes insulator to metallic transition above −20 °C.