Magnetotransport, thermophysical and magnetocaloric properties of manganite La-=SUB=-0.8-=/SUB=-Ag-=SUB=-0.1-=/SUB=-MnO-=SUB=-3-=/SUB=- in magnetic fields up to 8 T

Abstract

The electrical resistance, heat capacity, thermal conductivity, thermal conductivity and magnetocaloric effect of the polycrystalline sample La0.8Ag0.1MnO3 were measured in the temperature range 77-350 K and in magnetic fields up to 8 T. It is shown that electrical resistance in the paramagnetic phase can be explained within the framework of the concept of small-radius polarons with an activation energy of EP=119 meV, and the behavior of electrical resistance in the low-temperature ferromagnetic phase suggests the existence of several scattering mechanisms. The observed large magnitude of the magnetoresistive effect at low temperatures is explained by the intergranular tunneling of conduction electrons. An anomalous abrupt change in the lattice heat capacity during the ferromagnetic-paramagnetic phase transition was detected. The increase in thermal conductivity and thermal conductivity observed below the Curie temperature TC is associated with the scattering of phonons by local Jahn-Teller distortions, which weaken during the transition to the ferromagnetic phase. The magnetocaloric effect in a magnetic field of 8 T reaches a value of Delta Delta Tad=4 K, and the value of the efficiency of magnetic cooling in the same field is 261.6 J/kg. Keywords: manganites, electrical resistance, heat capacity, thermal conductivity, thermal conductivity, magnetocaloric effect. Keywords: manganites, electrical resistance, heat capacity, thermal conductivity, thermal conductivity, magnetocaloric effect.