Effect of Structural Transition on Magnetic Properties of Fe-Doped Nanocrystalline La0.7Te0.3Mn1-xFexO₃ (x 0.2, 0.4 and 0.5).

Abstract

Structural, magnetic and magnetocaloric properties of electron-doped nanocrystalline La0.7Te0.3Mn1-xFexO₃ (x ═ 0.2, 0.4 and 0.5) samples synthesized by the sol-gel method were investigated. All samples were described by X-ray diffraction (XRD) technique at room temperature confirming the single phase nature with no detectable secondary or impurity phase. With the increase in Fe concentration from 0.2 to 0.5, a structural transition from rhombohedral to orthorhombic was observed. The temperature dependent magnetization measurements revealed that with an increase in the Fe concentration from x ═ 0.2 to x ═ 0.5, Curie temperature (TC) decreases from 140 K to 71 K. Arrott plots revealed a second order magnetic phase transition for all the samples. The magnetic entropy change |ΔSM| for all the samples were calculated using field dependent magnetization data and the calculated maximum entropy change |ΔSmaxM| values have been found to be 1.18 Jkg-1K-1, 0.76 Jkg-1K-1 and 0.42 Jkg-1K-1 for a field change of 5 T for x ═ 0.2, 0.4 and 0.5 respective samples. The magnetoclaoric property of the electron-doped manganite is influenced by the Fe substitution at Mn-site as shown by the magnetization results. A detailed critical exponent analysis has been carried out for the nanocrystalline La0.7Te0.3Mn0.8Fe0.2O₃ sample using scaling hypothesis. The deduced critical exponent values for the nanocrystalline La0.7Te0.3Mn0.8Fe0.2O₃ samples were observed to be near that of 3D Heisenberg model.