Magnetic-phase transition in the magnetic-polaron system studied with the Monte Carlo method: Anomalous specific heat of EuB6

Abstract

We have investigated the phase transition in the magnetic-polaron system to understand the anomalous behavior of the specific heat C in EuB6 near the magnetic-phase transition temperature T-C. By employing the exact diagonalization and the Monte Carlo method, we have found a new temperature scale T-p, at which C has its maximum value and the magnetic polarons become percolated. We have demonstrated that, upon cooling, the isolated magnetic polarons become linked to yield the finite magnetization at T-C, and then the linked magnetic polarons eventually merge to show the percolating behavior with the C peak at T-p (T-p < T-C). The validity of the Fisher-Langer relation in the magnetic-polaron system is also discussed.