Effect of Negative Pressure on the Prototypical Itinerant Magnet MnSi

TL;DR

This study explores how negative pressure, induced by Al and Ga substitution, affects the magnetic and charge transport properties of MnSi, revealing increased Curie temperature, altered skyrmion stability, and temperature-dependent anomalous Hall effects.

Contribution

It demonstrates how chemical substitution creates negative pressure in MnSi, leading to significant changes in magnetic behavior and charge transport, including skyrmion phase stability and Hall effect variations.

Findings

Increased Curie temperature and ordered moment with substitution

Expanded temperature and field range of skyrmion stability

Temperature-dependent anomalous Hall conductivity sign and magnitude

Abstract

The evolution of the magnetic and charge transport properties of itinerant magnetic metal MnSi with the substitution of Al and Ga on the Si site is investigated. We observe an increase in unit cell volume indicating that both Al and Ga substitutions create negative chemical pressure. There are substantial increases in the Curie temperature and the ordered moment demonstrating that the substitutions give the magnetism a more local character. The substitutions also increase the range of temperature and field where the skyrmion phase is stable due to a change in the character of the magnetism. In contrast to the behavior of pure MnSi and expectations for the intrinsic anomalous Hall effect, we find a significant temperature dependence to the magnitude and sign of anomalous Hall conductivity constant in Al or Ga substituted samples. This temperature dependence likely reflects changes in the spin-orbit coupling strength with temperature, which may have significant consequences on the helical and skyrmion states. Overall, we observe a continuous evolution of magnetic and charge transport properties through positive to negative pressure