Heat diffusivity of La1−xCaxMnO3 epitaxial layers

Abstract

The Seebeck effect and the thermal diffusivity of La0.67Ca0.33MnO3−δ were investigated in the temperature range 35<T<300 K and in particular in the regime of the high magnetoresistance and maximum resistivity ρmax. We find a sign change of the thermoelectric power S(T) and a step in heat conductivity near ρmax which we attribute to a temperature-induced metal–insulator transition at about 80 K, suggesting that the large giant magnetoresistance found in these substances is due to a field-induced metal–insulator transition.

Heat capacities of (Ca,Ln)MnO3 (Ln=Pr, Nd and Sm)

“…The magnetic contribution of heat capacity for these compounds was estimated from the value of the spontaneous magnetization by similar method by Tanaka and Mituhashi [13]. In this case the stabilization energy for the interaction is given as follows:…”

“…The magnetic specific heat and Debye temperature of (La 0.8 Ca 0.2 )MnO 3+y using laser flash method was measured by Tamura and Kuriyama [11] and stoichiometric (La 0.8 Ca 0.2 )MnO 3 had a thermal anomaly near 180 K. Tanaka and Mitsuhashi [12] attempted theoretical calculation of magnetic heat capacity for (La 0.8 Ca 0.2 )MnO 3 . Liebe et al [13] reported about heat diffusivity of La 1−x Ca x MnO 3 .…”

“…Although data of thermodynamic properties is inevitable for the discussion on the phase stability and the reactivity with the other compound, only a few thermodynamic properties for (A,Ln)MnO 3 have been reported [11][12][13]. The magnetic specific heat and Debye temperature of (La 0.8 Ca 0.2 )MnO 3+y using laser flash method was measured by Tamura and Kuriyama [11] and stoichiometric (La 0.8 Ca 0.2 )MnO 3 had a thermal anomaly near 180 K. Tanaka and Mitsuhashi [12] attempted theoretical calculation of magnetic heat capacity for (La 0.8 Ca 0.2 )MnO 3 .…”

Unusual electroresistive effect in ceramic La0.49Ca0.51MnO3

“…For LCMO, the comparison of epitaxial layers [10,11] and ceramic samples [7,12] yields the same equivalency. There are, of course, exceptions from these rules if the parameter ranges of the interface layers cease to overlap; for example when the layer thickness gets very low (<150 nm), so that the nature of the connecting interfaces becomes the controlling factor.…”

Origin of Hysteresis in La0.67Ca0.33MnO3

“…The most elusive aspect of the manganite system has been whether there is any clear evidence to support the claim that the ferromagnetic to paramagnetic transition is first order. We have investigated hysteresis, which may impact on use of these materials as refrigerants, in terms of thermal management as the manganites are known to have low thermal conductivity [12], [38][39] and this needs to be addressed. The system appears to show no intrinsic hysteresis.…”