Ferromagnetism mediated by few electrons in a semimagnetic quantum dot

TL;DR

This paper demonstrates that a single electron in a semimagnetic quantum dot can induce ferromagnetism among Mn spins, with the effect persisting above 1 Kelvin and strongly depending on electron parity.

Contribution

It reveals how a single conduction electron can mediate ferromagnetism in a quantum dot, a phenomenon not observed in bulk materials.

Findings

Single electron induces collective Mn spin magnetization.

Ferromagnetism persists above 1 Kelvin.

Magnetic behavior depends on electron parity.

Abstract

A (II,Mn)VI diluted magnetic semiconductor quantum dot with an integer number of electrons controlled with a gate voltage is considered. We show that a single conduction band electron is able to induce a spontaneous collective magnetization of the Mn spins, overcoming the short range antiferromagnetic interactions. The carrier mediated ferromagnetism in the dot survives at temperatures above 1 Kelvin, two orders of magnitude larger than the Curie temperature for the same material in bulk. The magnetic behavior of the dot depends dramatically on the parity of the number of injected electrons.