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

• Published in: IEEE transactions on magnetics Vol. 50; no. 11; pp. 1 - 4
• Main Authors: Antonak, Marek, Mihalik, Marian, Mihalik, Matus, Zentkova, Maria, Gritzner, Gerhard
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-11-2014; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Colassal magnetoresistance; Cooling; Heat; Lanthanum compounds; Magnetic field measurement; Magnetic fields; Magnetic flux; Magnetic moments; Magnetism; Phase transitions; Temperature dependence; pressure effect; Colossal magneto-resistance; magnetic entropy change; manganites
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2014.2318076

Electrical resistance R, heat capacity C, ac susceptibility, and magnetic moment of orthorhombic La 0.85 Ag 0.15 MnO 3 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 μ 0 AH = 5 T and both values -ΔS = 5.85 Jkg -1 K -1 (heat capacity) and -ΔS = 5.80 Jkg -1 K -1 (magnetic moment) are comparable. Hydrostatic pressure of 0.84 GPa leads to an enhancement of -ΔS approximately about 14%.