Magnetic Heat Capacity of Monoclinic (La_0.8Ca_0.2)MnO₃

抄録

Heat capacity of (La_0.8Ca_0.2)MnO₃ was measured by a laser-flash method. An anomaly of the heat capacity with the entropy change of ΔS=0.54 cal/mol·K was observed near magnetic transition temperature T_c. By assuming a simple Heisenberg model, an exchange interaction constant was determined to be J=8.0 cal/mol. The value of the magnetic heat capacity at T_c was ΔC=4.2R, which is nearly equal to the value calculated from a double exchange model. The analysis of the heat capacity near T_c showed clearly that the transition is of second order and induced only by the change of electronic state.