The effect of longitudinal spin-fluctuations on high temperature properties of Co$_3$Mn$_2$Ge

TL;DR

This paper demonstrates that including longitudinal spin fluctuations in ab initio calculations significantly improves the accuracy of predicted high-temperature magnetic properties of Co$_3$Mn$_2$Ge, especially the Curie temperature.

Contribution

It introduces a simple model for incorporating longitudinal spin fluctuations into ab initio calculations, revealing their crucial role in magnetic entropy and exchange interactions.

Findings

Longitudinal spin fluctuations induce medium-sized local moments on Co atoms.

Including LSF aligns calculated Curie temperature with experimental data.

LSF significantly affects magnetic entropy and exchange interactions.

Abstract

It is demonstrated that thermally induced longitudinal spin fluctuations (LSF) play an important role in itinerant Co$_3$Mn$_2$Ge at an elevated temperature. The effect of LSF is taken into account during {\it ab initio} calculations via a simple model for the corresponding entropy contribution. We show that the magnetic entropy leads to the appearance of a medium size local moment on Co atoms. As a consequence, this leads to a renormalization of the magnetic exchange interactions with a quite substantial impact upon the calculated Curie temperature. Taking LSF into account, the calculated Curie temperature can be brought to be in good agreement with the experimental value.