Field dependent specific-heat of rare earth manganites

The low-temperature specific heat C(H) of several rare-earth manganites (La0.7Sr0.3MnO3, Nd0.5Sr0.5MnO3, Pr0.5Sr0.5MnO3, La0.67Ca0.33MnO3, La0.5Ca0.5MnO3, La0.45Ca0.55MnO3 and La0.33Ca0.67MnO3) was measured as a function of magnetic field. We observed behavior consistent with thermodynamic expectations, i.e., C(H) decreases with field for ferromagnetic metallic compounds by an amount which is in quantitative agreement with spin-wave theory. We also find that C(H) increases with field in most compounds with a charge-ordered antiferromagnetic ground state. In compounds which show evidence of a coexistence of ferromagnetic metallic and antiferromagnetic charge-ordered states, C(H) displays some unusual non-equilibrium effects presumably associated with the phase-separation of the two states. We also observe a large anomalous low-temperature specific heat at the doping-induced metal–insulator transition (at x=0.50) in La1−xCaxMnO3.