Curie point singularity in the temperature derivative of resistivity in (Ga,Mn)As

TL;DR

This study identifies a unique singularity in the temperature derivative of resistivity at the Curie point in (Ga,Mn)As ferromagnetic semiconductors, revealing critical spin fluctuation effects near the phase transition.

Contribution

It reports the observation of a Curie point singularity in $d ho/dT$ in (Ga,Mn)As, highlighting the role of short-range correlated spin fluctuations, which differs from conventional magnetic semiconductors.

Findings

Singularity in $d ho/dT$ at the Curie point.

Distinct behavior from conventional magnetic semiconductors.

Critical role of short-range spin fluctuations.

Abstract

We observe a singularity in the temperature derivative $d\rho/dT$ of resistivity at the Curie point of high-quality (Ga,Mn)As ferromagnetic semiconductors with $T_c$'s ranging from approximately 80 to 185 K. The character of the anomaly is sharply distinct from the critical contribution to transport in conventional dense-moment magnetic semiconductors and is reminiscent of the $d\rho/dT$ singularity in transition metal ferromagnets. Within the critical region accessible in our experiments, the temperature dependence on the ferromagnetic side can be explained by dominant scattering from uncorrelated spin fluctuations. The singular behavior of $d\rho/dT$ on the paramagnetic side points to the important role of short-range correlated spin fluctuations.