Layer-dependence of macroscopic and atomic magnetic correlations in Co/Pd multilayers

N Soriano,A Gómez,E Navarro,C Quirós,E M González,I Montoya,B Mora,M Vélez,P Gargiani,J L Vicent,J M Alameda,M Valvidares,R Morales,C Redondo,J Del Valle,F Gálvez,V Rollano

doi:10.1063/5.0010066

Abstract

The development of multilayered materials with engineered magnetic properties compels a deep knowledge of physical properties at the atomic scale. The magnetic anisotropy is a key property in these materials. This work accounts for the magnetic anisotropy energy and its correlation with atomic properties of Co/Pd multilayers with the number of Co/Pd repetitions. Magnetometry measurements confirm stronger perpendicular magnetic anisotropy energies as the number of repetitions increases up to 40. However, the intrinsic anisotropy, related to the Co–Pd orbital hybridization and spin–orbit coupling, saturates at 15 repetitions. This finding is supported by x-ray magnetic circular dichroism analysis that reveals a direct correlation of the atomic Co and Pd orbital magnetic moments and the effective anisotropy of the system. The proximity effect that accounts for the Pd induced magnetization, along with the increasing Co moment, provides a suitable mechanism for the observed anisotropy energy layer dependence.

Highlights

E scitation.org/journal/adv bulk properties of the film.17,18 The symmetry-breaking at the surface induces the so-called surface anisotropy perpendicular to the sample plane, competing with the shape anisotropy.19–25 Atoms near the surface or interface experience a reduced symmetry and different bonds than those in the bulk, which lead to a variety of magnetic phenomena such as out of plane anisotropy, enhancement of magnetic moments, and magnetic polarization of non-magnetic elements.26–30 A key factor for these phenomena is the spin–orbit interaction that couples spins to the electronic orbits of the crystal lattice
The intrinsic anisotropy, related to the Co–Pd orbital hybridization and spin–orbit coupling, saturates at 15 repetitions. This finding is supported by x-ray magnetic circular dichroism analysis that reveals a direct correlation of the atomic Co and Pd orbital magnetic moments and the effective anisotropy of the system
This work reports on the evolution of the magnetic anisotropy energy, the in the sample plane (IP) and out of plane (OoP) anisotropy, and its microscopic origin in Co/Pd multilayers as a function of the number of repetitions (n)

Summary

Introduction

E scitation.org/journal/adv bulk properties of the film.17,18 The symmetry-breaking at the surface induces the so-called surface anisotropy perpendicular to the sample plane, competing with the shape anisotropy.19–25 Atoms near the surface or interface experience a reduced symmetry and different bonds than those in the bulk, which lead to a variety of magnetic phenomena such as out of plane anisotropy, enhancement of magnetic moments, and magnetic polarization of non-magnetic elements.26–30 A key factor for these phenomena is the spin–orbit interaction that couples spins to the electronic orbits of the crystal lattice. This work accounts for the magnetic anisotropy energy and its correlation with atomic properties of Co/Pd multilayers with the number of Co/Pd repetitions.

Results

Conclusion