Interplay between Mesoscopic and Microscopic Fluctuations in Ferromagnets

TL;DR

This paper investigates how mesoscopic paramagnetic fluctuations influence ferromagnetic properties, revealing their impact on phase transition order, spin-wave behavior, and critical parameters, highlighting complex interactions between mesoscopic and microscopic fluctuations.

Contribution

It introduces a model showing how mesoscopic fluctuations affect ferromagnetic phase transitions and their interplay with microscopic magnon fluctuations.

Findings

Mesoscopic fluctuations reduce magnetization and soften spin waves.

They extend the parameter region for first-order phase transitions.

Fluctuations lower the critical point and alter phase transition characteristics.

Abstract

A model of a ferromagnet is considered, in which there arise mesoscopic fluctuations of paramagnetic phase. The presence of these fluctuations diminishes the magnetization of the ferromagnet, softens the spin-wave spectrum, increases the spin-wave attenuation, shortens the magnon free path, lowers the critical point, and can change the order of phase transition. A special attention is paid to the interplay between these mesoscopic paramagnetic fluctuations and microscopic fluctuations due to magnons. One of the main results of this interplay is an essential extension of the region of parameters where the ferromagnet-paramagnet phase transition is of first order.