Suppression of Metamagnetic Transitions of Martensitic Type by Particle Size Reduction in Charge-Ordered La0.5Ca0.5MnO3

Abstract

In this paper, we have studied the effect of size reduction on charge ordering (CO) and magnetic phase separation in La0.5Ca0.5MnO3. The magnetic ground state at low temperature shifts from ferromagnetic (nanoparticles) to CO-antiferromagnetic (bulk) with increasing annealing temperature. The studied samples exhibit relevant phenomena such as Griffiths phase and training effect. Magnetic field cycling can stabilize ferromagnetic or antiferromagnetic domains, depending on the temperature value as well as the sample’s nature. For the compound sintered at 1200 °C, step-like metamagnetic transitions of martensitic type were observed at 4 K, indicating the presence of weak spin-phonon coupling. The disappearance of magnetic phase separation at 4 K (the sample is purely antiferromagnetic) can be a possible origin for the occurrence of such transitions. Lowering the sintering temperature leads to the disappearance of martensitic transitions. The obtained results indicate that the occurrence of step-like metamagnetic transition of martensitic type necessarily requires the onset of a long-range CO-antiferromagnetic state.