Random telegraph noise from magnetic nanoclusters in the ferromagnetic semiconductor (Ga,Mn)As

TL;DR

This study investigates low-frequency electrical noise in ferromagnetic (Ga,Mn)As, revealing magnetic clusters formed by Mn defects that influence transport properties, especially under strong localization conditions.

Contribution

It uncovers the role of Mn interstitials in forming magnetic nanoclusters that cause random telegraph noise in (Ga,Mn)As, a novel insight into defect-related magnetic phenomena.

Findings

Enhanced low-temperature noise in (Ga,Mn)As.

Lorentzian noise spectra linked to magnetic clusters.

Magnetic clusters modulate hole transport based on defect interactions.

Abstract

Measurements of the low frequency electrical noise in the ferromagnetic semiconductor (Ga,Mn)As reveal an enhanced integrated noise at low temperature. For moderate localization, we find a 1/f normalized power spectrum density over the entire range of temperatures studied (4.2K < T < 70K). However, for stronger localization and a high density of Mn interstitials, we observe Lorentzian noise spectra accompanied by random telegraph noise. Magnetic field dependence and annealing studies suggest that interstitial Mn defects couple with substitutional Mn atoms to form nanoscale magnetic clusters characterized by a net moment of about 20 Bohr magnetons whose fluctuations modulate hole transport.