Lieb-Mattis ferrimagnetism in diluted magnetic semiconductors

TL;DR

This paper demonstrates that long-range ferrimagnetic order can be achieved in diluted magnetic semiconductors at low impurity concentrations if the impurities form specific superstructures satisfying Lieb-Mattis conditions, with implications for magnetic properties and phase transitions.

Contribution

It introduces a method to realize ferrimagnetism in semiconductors through impurity superstructures based on Lieb-Mattis theorem, providing explicit lattice examples and analyzing magnetic behavior.

Findings

Ferrimagnetic order possible at low impurity concentrations.

Superstructures exhibit enhanced magnetic response.

Quantum transitions occur under high magnetic fields.

Abstract

We show the possibility of long-range ferrimagnetic ordering with a saturation magnetisation of the order of 1 Bohr magneton per spin for arbitrarily low concentration of magnetic impurities in semiconductors, provided that the impurities form a superstructure satisfying the conditions of the Lieb-Mattis theorem. Explicit examples of such superstructures are given for the wurtzite lattice, and the temperature of ferrimagnetic transition is estimated from a high-temperature expansion. Exact diagonalization studies show that small fragments of the structure exhibit enhanced magnetic response and isotropic superparamagnetism at low temperatures. A quantum transition in a high magnetic field is considered and similar superstructures in cubic semiconductors are discussed as well.