Investigation of doping effect on structural, magnetic and magnetoresistance properties by Ru doping in the manganite La0.6Ce0.05Ba0.35Mn1-xRuxO3 (0 ≤ x ≤ 0.2)

Abstract

During this study, we were conducted to analyze the properties of structural, magnetic, magnetocaloric, electrical resistivity and magnetoresistance (by applying magnetic fields of zero, 2 and 5T) of ceramics La0.6Ce0.05Ba0.35Mn1-xRuxO3 (0 ≤ x ≤ 0.2). These samples are prepared by solid-state reaction. The compounds have simple rhombohedral structure R-3c space group. Arrot curves display that all materials exhibit a second-order magnetic transition from ferromagnetic to paramagnetic order. All the manganites synthesized show a maximum variation in magnetic entropy (|ΔSM|) with values between 6.2 J/kg.K for x = 0 and 3.4 J/kg.K for x = 0.2. In addition, the relative cooling power (RCP) values are very important (160 J/kg for x = 0 to 248 J/kg for x = 0.2). Environment-friendly compounds applied in the domestic refrigeration.The samples La0.6Ce0.05Ba0.35Mn1-xRuxO3 (0 ≤ x ≤ 0.1) show a transition from ferromagnetic-metal (FM) to paramagnetic-insulator (MI). Sample La0.6Ce0.05Ba0.35Mn0.8Ru0.2O3 exhibits semiconductor behavior over the entire temperature range. The metallic conduction is due to the diffusion of electrons (by the phonons and the grain boundaries) while the semiconducting behavior is due to the attendance of polarons. The curves of the compounds (0 ≤ x ≤ 0.1) in the metallic region (T < Tp), have been fitted to the equationρ=αT2+βT5+1(γ+δT1/2). For the high temperature, the semiconductor region was fitted by the small polaron hopping model (ASPH) and by the variable hopping range model (VRH). The electrical resistivity behavior indicates that the substitution of Ru3+ ions weakened the double exchange process and improved the Jahn-Teller effect. Studies of magnetoresistance (MR) under 2 and 5 T magnetic field show two kinds of contribution: one is intrinsic MR and the other is extrinsic MR.