Evidence of magneto-structural coupling affecting magnetic anisotropy in a cobalt nano-composite

Abstract

By investigating temperature dependent structural and magnetic properties of cobalt (Co) embedded within nanoporous anodized alumina template, we observe changes in the easy axis of Co magnetization and an unusual increase in its saturation magnetization below a temperature T . Analysis of our M(H) data reveals that the magnetized volume of the sample increases rapidly as T falls below T. To understand these features we perform micro-magnetic simulations for a single Co-nanopillar wherein by varying its magneto-crystalline anisotropy energy we are able to show that the changes observed near T are related to the changes in the magnetic anisotropy of the nanopillar. We propose crystallographic structural distortions trigger changes in the balance between shape and magneto-crystalline anisotropy in our nanopillar. Our results suggest interplay between magnetism, structure and magnetic anisotropy in low dimensional Co-nanopillars, which can be modified with temperature of the system.