Magnetic properties of Mn impurities on GaAs (110) surfaces

TL;DR

This study uses density functional theory to analyze the magnetic properties and anisotropy of Mn impurities on GaAs (110) surfaces, revealing how surface effects and correlations influence magnetic behavior.

Contribution

It provides new insights into the magnetic anisotropy and exchange interactions of Mn impurities on GaAs surfaces, emphasizing the roles of surface symmetry, correlations, and spin-orbit effects.

Findings

Mn acceptor-hole wavefunction is more localized on the surface

Magnetic anisotropy energy is about 1 meV for isolated Mn

Mn pairs tend to align their spins parallel, with exchange energy depending on orientation

Abstract

We present a computational study of individual and pairs of substitutional Mn impurities on the (110) surface of GaAs samples based on density functional theory. We focus on the anisotropy properties of these magnetic centers and their dependence on on-site correlations, spin-orbit interaction and surface-induced symmetry-breaking effects. For a Mn impurity on the surface, the associated acceptor-hole wavefunction tends to be more localized around the Mn than for an impurity in bulk GaAs. The magnetic anisotropy energy for isolated Mn impurities is of the order of 1 meV, and can be related to the anisotropy of the orbital magnetic moment of the Mn acceptor hole. Typically Mn pairs have their spin magnetic moments parallel aligned, with an exchange energy that strongly depends on the pair orientation on the surface. The spin magnetic moment and exchange energies for these magnetic entities are not significantly modified by the spin-orbit interaction, but are more sensitive to on-site correlations. Correlations in general reduce the magnetic anisotropy for most of the ferromagnetic Mn pairs.