Effect of surface pinning on magnetic nanostuctures

TL;DR

This paper investigates how surface pinning influences magnetic properties of nanostructures, revealing increased exchange bias with pinning density and spin fraction, and extends findings across various shapes, sizes, and spin models.

Contribution

It introduces a simple surface model to analytically explain surface pinning effects on hysteresis and exchange bias in diverse magnetic nanostructures.

Findings

Exchange bias increases with pinning density.

Asymmetry in hysteresis is more prominent in inverse core-shell structures.

Effects are consistent across different shapes, sizes, and spin models.

Abstract

Magnetic nanostructures are often considered as highly functional materials because they exhibit unusual magnetic properties under different external conditions. We study the effect of surface pinning on the core-shell magnetic nanostuctures of different shapes and sizes considering the spin-interaction to be Ising-like. We explore the hysteresis properties and find that the exchange bias, even under zero field cooled conditions, increases with increase of, the pinning density and the fraction of up-spins among the pinned ones. We explain these behavior analytically by introducing a simple model of the surface. The asymmetry in hysteresis is found to be more prominent in a inverse core-shell structure, where spin interaction in the core is antiferromagnetic and that in the shell is ferromagnetic. These studied of inverse core-shell structure are extended to different shapes, sizes, and different spin interactions, namely Ising, XY- and Heisenberg models in three dimension. We also briefly discuss the pinning effects on magnetic heterostructures.