Bose-Einstein Condensation of Confined Magnons in Nanostructures

Lawrence H Bennett,Edward Della Torre

doi:10.4236/jmp.2014.58081

Abstract

A number of diverse kinds of magnetic experiments are shown to lead to the observation of a Bose-Einstein condensation of magnons in some nanostructures, especially in Fe and in Co/Pt. The experiments include 1) the measurement of magnetic aftereffect, 2) measurements of Neel’s fluctuation field, including an estimate of activation volume, 3) the measurement of the energy gap which provides a lower limit on the BEC temperature, 4) using Lagrange multipliers in the quantum thermodynamics of magnons, and 5) the observation of a visible anomaly in the Bloch T3/2 law for the temperature dependence of magnetization of nanostructured ferromagnets.

Highlights

The occupation of a single quantum state by a large fraction of bosons at low temperatures [1] was predicted by Bose and Einstein in the 1920s
A promising extension is to magnons—spin-wave quanta that behave as bosonic quasiparticles—in magnetic nanoparticles
This system has unique characteristics differentiating it from atomic BEC, creating the potential for a whole new variety of interesting behaviors and applications that include high-temperature Bose-Einstein condensation and novel nanomagnetic devices

Summary

Introduction

The occupation of a single quantum state by a large fraction of bosons at low temperatures [1] was predicted by Bose and Einstein in the 1920s. The quest for Bose-Einstein condensation (BEC) in a dilute atomic gas was achieved [2] in 1995 using laser-cooling to reach ultra-cold temperatures of 20 nK. BEC of dilute atomic gases, regularly created in a number of laboratories around the world, have led to a wide range of unanticipated applications. A promising extension is to magnons—spin-wave quanta that behave as bosonic quasiparticles—in magnetic nanoparticles. This system has unique characteristics differentiating it from atomic BEC, creating the potential for a whole new variety of interesting behaviors and applications that include high-temperature Bose-Einstein condensation and novel nanomagnetic devices. Recent research [4]-[10]

Methods

Results

Discussion

Conclusion