Magnetocaloric Effect of La0.85Ag0.15MnO3 Under Pressure

Electrical resistance R, heat capacity C, ac susceptibility, and magnetic moment of orthorhombic La_0.85Ag_0.15MnO₃ ceramic were investigated in magnetic fields with flux density up to 5 T and in high hydrostatic pressures up to 0.9 GPa. Sharp lambda-like anomalies in R(T) and C(T) indicate ferromagnetic (FM)-paramagnetic transition. Magnetic field shifts these anomalies to higher temperature and smears them out confirming FM origin of the ordering. Magneto-resistance is negative and large reaching maximal value of about 70% for field with flux density of 5 T at the magnetic phase transition. The magnetic phase transition is accompanied with anomalies at 219.5 K in χ\´(T) and at 221 K in χ"(T). The Curie temperature T_C increases with applied pressure with the rate dT_C/dp = 14.2 K/GPa. Magnetocaloric effect was evaluated from the magnetic entropy change ΔS, which was determined independently from heat capacity and magnetic moment measurements. The maximal values were obtained for μ₀AH = 5 T and both values -ΔS = 5.85 Jkg^-1K^-1 (heat capacity) and -ΔS = 5.80 Jkg^-1K^-1 (magnetic moment) are comparable. Hydrostatic pressure of 0.84 GPa leads to an enhancement of -ΔS approximately about 14%.