Regular Article

Size effects of the magnetic anisotropy of fcc cobalt nanoparticles embedded in copper

¹ Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, 69622 Villeurbanne, France
² Univ. Estadual Campinas Unicamp, Inst. Fis. Gleb Wataghin, Rua Sergio Buarque de Holanda 777, 13083859 Campinas, SP, Brazil

^a e-mail: matthias.hillenkamp@univ-lyon1.fr

Received: 2 May 2017
Received in final form: 26 October 2017
Published online: 14 December 2017

Abstract

Cobalt nanoparticles embedded in copper matrices show strong size effects in the magnetic anisotropy with a non-monotonous dependence on the particle diameter. In this article we discuss quantitative values of the magnetic anisotropy in the frame of two models: in small clusters the surface anisotropy contribution dominates whereas larger particles ( >3 nm diameter) have an elliptic shape leading to increased shape anisotropy. The crystalline structure of the particles is shown to be face-centered cubic, justifying that the magneto-crystalline anisotropy can be neglected.