Surface induced suppression of magnetization in nanoparticles

Abstract

A model based on competing exchange interactions is presented for the investigation of nanoparticle magnetization. The ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions contribute differently at the nanoparticle surface and interior, leading to reduced ferromagnetic order at the surface. This model predicts an unconventional temperature dependence of magnetization and a surface magnetically 'dead layer'. This is confirmed by temperature dependent magnetization and Mössbauer measurements of FePt nanoparticles. The effects are sensitive to particle size and surface terminations.