EPR and ferromagnetism in diluted magnetic semiconductor quantum wells

TL;DR

This paper develops a theory of collective spin excitations in quasi-two-dimensional diluted magnetic semiconductors, explaining experimental EPR spectra and discussing conditions for ferromagnetism in quantum wells.

Contribution

It introduces a theoretical framework for understanding collective spin behavior and ferromagnetism in DMS quantum wells, linking experimental observations with magnetic interactions.

Findings

Explains large Knight shift via collective coupling

Provides insights into ferromagnetism in (II,Mn)VI quantum wells

Discusses temperature conditions for ferromagnetic order

Abstract

Motivated by recent measurements of electron paramagnetic resonance (EPR) spectra in modulation-doped CdMnTe quantum wells, [F.J. Teran {\it et al.}, Phys. Rev. Lett. {\bf 91}, 077201 (2003)], we develop a theory of collective spin excitations in quasi-two-dimensional diluted magnetic semiconductors (DMSs). Our theory explains the anomalously large Knight shift found in these experiments as a consequence of collective coupling between Mn-ion local moments and itinerant-electron spins. We use this theory to discuss the physics of ferromagnetism in (II,Mn)VI quantum wells, and to speculate on the temperature at which it is likely to be observed in n-type modulation doped systems.