Magnetization reversal study along easy and hard axes in a superferromagnet

Abstract

In a dense ensemble of magnetic nanoparticles, but still below physical percolation, sufficiently strong interactions can be experienced to form a superferromagnetic (SFM) state. SFM domains in a non-percolated nanoparticle assembly are expected to be similar to conventional FM domains in a continuous film, with the decisive difference that the atomic spins are replaced by the superspins of the single-domain nanoparticles. In this article, Kerr microscopy has been performed on a granular multilayer [Co80Fe20(1.3nm)/Al2O3(3nm)]10 to study the magnetization reversal processes. We show that the magnetization reversal occurs via domain wall motion followed by subsequent nucleation and coherent rotation when measured along the easy and hard axis, respectively.