Low-temperature magnetothermodynamics of Pr_0.7Ca_0.3MnO₃

Abstract

We present a detailed magnetothermal study of Pr_0.7Ca_0.3MnO₃, a perovskite manganite in which an insulator-metal transition can be driven by magnetic field but also by pressure, visible light, X-rays or high currents. We find that the field-induced transition is associated with a large release of energy which accounts for its strong irreversibility. In the ferromagnetic metallic state, specific heat and magnetization measurements indicate a much smaller spin-wave stiffness than seen in any other ferromagnetic manganite, which we explain in terms of ferromagnetism among the Pr moments. The Pr ferromagnetism also appears to influence the low-temperature thermodynamic phase diagram of this material and the uniquely sensitive metastability of the insulating state.