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

TL;DR

This study reports the observation of spontaneous magnetization above the Curie temperature in specific manganite compounds, linking it to a transition between magnetic phases influenced by temperature and magnetic field.

Contribution

It provides new insights into magnetic phase transitions in La-based manganites, identifying a temperature $T^*$ where spontaneous magnetization persists above $T_C$.

Findings

Spontaneous magnetization observed above $T_C$ up to $T^*$.

$T^*$ related to low-temperature magnetic phase transition.

Magnetic field induces transition from high to low-temperature magnetic phases.

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.