Ising Quantum Hall Ferromagnet in Magnetically Doped Quantum Wells

TL;DR

This paper reports the observation of an Ising quantum Hall ferromagnet in a magnetically doped quantum well with a Curie temperature up to 2 K, highlighting the role of Landau level crossing and spin interactions.

Contribution

It presents the first experimental observation of an Ising quantum Hall ferromagnet in (Cd,Mn)Te heterostructures with detailed analysis of magnetic and electronic interactions.

Findings

Observation of quantum Hall ferromagnet with $T_C$ up to 2 K

Critical behavior of resistance spikes near $T_C$

Influence of Coulomb interactions and s-d coupling on ferromagnetism

Abstract

We report on the observation of the Ising quantum Hall ferromagnet with Curie temperature $T_C$ as high as 2 K in a modulation-doped (Cd,Mn)Te heterostructure. In this system field-induced crossing of Landau levels occurs due to the giant spin-splitting effect. Magnetoresistance data, collected over a wide range of temperatures, magnetic fields, tilt angles, and electron densities, are discussed taking into account both Coulomb electron-electron interactions and s$-$d coupling to Mn spin fluctuations. The critical behavior of the resistance ``spikes'' at $T \to T_C$ corroborates theoretical suggestions that the ferromagnet is destroyed by domain excitations.