Absence of weak antilocalization in ferromagnetic films

TL;DR

This study investigates how ferromagnetism affects electron localization in ultrathin amorphous Ni and Fe films, revealing that magnetic order suppresses spin-orbit effects that cause weak antilocalization.

Contribution

It provides experimental evidence that ferromagnetic order suppresses weak antilocalization in ultrathin films, confirming theoretical predictions.

Findings

Non-ferromagnetic films show positive magnetoresistance due to weak antilocalization.

Ferromagnetic films exhibit negative magnetoresistance, indicating suppression of weak antilocalization.

Magnetic order reduces the influence of spin-orbit effects on localization phenomena.

Abstract

We present magnetoresistance measurements performed on ultrathin films of amorphous Ni and Fe. In these films the Curie temperature drops to zero at small thickness, making it possible to study the effect of ferromagnetism on localization. We find that non-ferromagnetic films are characterized by positive magnetoresistance. This is interpreted as resulting from weak antilocalization due to strong Bychkov-Rashba spin orbit scattering. As the films become ferromagnetic the magnetoresistance changes sign and becomes negative. We analyze our data to identify the individual contributions of weak localization, weak antilocalization and anisotropic magnetoresistance and conclude that the magnetic order suppresses the influence of spin-orbit effects on localization phenomena in agreement with theoretical predictions.