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

Electrical resistance R, heat capacity C, ac susceptibility, and magnetic moment of orthorhombic La0.85Ag0.15MnO3 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 chi'(T) and at 221 K in chi '' (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 Delta S, which was determined independently from heat capacity and magnetic moment measurements. The maximal values were obtained for mu(0)Delta H = 5 T and both values -Delta S = 5.85 Jkg(-1)K(-1) (heat capacity) and -Delta S = 5.80 Jkg(-1)K(-1) (magnetic moment) are comparable. Hydrostatic pressure of 0.84 GPa leads to an enhancement of -Delta S approximately about 14%.