Exchange interactions and Tc in rhenium doped silicon: DFT, DFT+U and Monte Carlo calculations

TL;DR

This study investigates the magnetic interactions and Curie temperature in rhenium-doped silicon using DFT, DFT+U, and Monte Carlo simulations, revealing ferromagnetic behavior at certain impurity concentrations and conditions.

Contribution

It provides a comparative analysis of exchange interactions in Re-doped silicon using DFT and DFT+U, and predicts Curie temperatures through Monte Carlo simulations.

Findings

All Re-Re interactions are ferromagnetic except dimers in DFT.

Dimer formations are nonmagnetic due to chemical bonding.

Room temperature ferromagnetism is predicted at specific impurity concentrations.

Abstract

Interactions between rhenium impurities in silicon are investigated by means of the density functional theory (DFT) and the DFT+U scheme. All couplings between impurities are ferromagnetic except the Re-Re dimers which in the DFT method are nonmagnetic, due to formation of the chemical bond supported by substantial relaxation of the geometry. The critical temperature is calculated by means of classical Monte Carlo (MC) simulations with the Heisenberg hamiltonian. The uniform ferromagnetic phase is obtained with the DFT exchange interactions at room temperature for the impurities concentration of 7%. With the DFT+U exchange interactions, the ferromagnetic clusters form above room temperature in MC samples containing only 3% Re.