Spontaneous magnetization above $T_C$ in polycrystalline La$_{0.7}$Ca$_{0.3}$MnO$_3$ and La$_{0.7}$Ba$_{0.3}$MnO$_3$

Abstract

In the present work, spontaneous magnetization is observed in the inverse magnetic susceptibility of La$_{0.7}$Ca$_{0.3}$MnO$_3$ and La$_{0.7}$Ba$_{0.3}$MnO$_3$ compounds above $T_C$ up to a temperature $T^*$. From information gathered from neutron diffraction, dilatometry, and high-field magnetization data, we suggest that $T^*$ is related to the transition temperature of the low-temperature (high magnetic field) magnetic phase. In the temperature region between $T^*$ and $T_C$, the application of a magnetic field drives the system from the high-temperature to low-temperature magnetic phases, the latter possessing a higher magnetization.