Critical behavior and magnetocaloric effect in Co-doped nanocrystalline La0.7Te0.3Mn1-xCoxO3

Abstract

We have explored the impact of cobalt doping on magnetic, magnetocaloric and electrical transport properties of the nanocrystalline La0.7Te0.3Mn1-xCoxO3 (0.1 ≤ x ≤ 0.5) samples synthesized using sol-gel method. The Rietveld refinement of the X-ray diffraction (XRD) patterns confirmed the rhombohedral crystal structure for x ≤ 0.2 samples and orthorhombic crystal structure for x ≥ 0.3 samples. The temperature dependence magnetization data proposed that each sample experienced a transition in phase from paramagnetic to ferromagnetic. The maximum values of magnetic entropy change |ΔSMmax| were calculated to be 2.93 Jkg−1K−1, 2.62 Jkg−1K−1, 2.04 Jkg−1K−1, and 1.71 Jkg−1K−1 for ΔH = 5 T respectively for x = 0.1, 0.2, 0.4, and 0.5 samples. Detailed critical exponent analysis was done for each sample and the nature of magnetic phase transition for x = 0.1 follows the 3D Heisenberg model, while for x = 0.2 and 0.3 pursue the mean field model. For x = 0.4 and 0.5, none of the models describe completely the magnetic phase transition. The temperature-dependent electrical resistivity ρ(T) data exhibit semi-conducting like behavior within the studied temperature range for x = 0.1 and 0.2 compositions. The magnetoresistance (MR %) values for x = 0.1 and x = 0.2 respectively were 44%, and 35% at a field change of 5 T around their respective transition temperatures. Relatively high values of |ΔSMmax| and MR% made the studied samples suitable for multifunctional device applications.