Correlation Functions of the Magnetization in Thin Films

TL;DR

This paper develops a microscopic approach to calculate the correlation functions of magnetization in thin ferromagnetic films, incorporating dissipation and fluctuations via a heat bath model, and relates it to macroscopic results.

Contribution

It introduces a functional formalism for correlation functions in thin films, explicitly coupling magnetization to a heat bath to account for dissipation and fluctuations.

Findings

Correlation functions depend strongly on the system-bath coupling.

The microscopic model relates to recent macroscopic results.

The approach provides a unified framework for understanding magnetization fluctuations.

Abstract

We calculate the correlation functions of uniform magnetization in thin ferromagnetic films for small deviations from equilibrium, by using a functional formalism. To take account of dissipation and fluctuations consistently, the magnetization is coupled to a bosonic heat bath. The correlation functions show strong dependence on the nature of the coupling between the bath and the system. Depending on what coupling we choose, we show how the recent results $(\text{J. Appl. Phys. 90, 5768 (2001); Phys. Rev. B 65, 172417 (2002)}) $ obtained by macroscopic methods can be related to the microscopic treatment adopted here.