Tuning the magnetic anisotropy of nanoparticles by metal capping

F. Luis; F. Bartolomé; F. Petroff; J. Bartolomé; L. M. García; C. Deranlot; H. Jaffrès; M. J. Martínez; P. Bencok; F. Wilhelm; A. Rogalev; N. B. Brookes

doi:10.1209/epl/i2006-10242-2

All issues

Volume 76 / No 1 (October 2006)

Europhys. Lett., 76 1 (2006) 142-148

Abstract

Issue		Europhys. Lett. Volume 76, Number 1, October 2006


Page(s)		142 - 148
Section		Condensed matter: electronic structure, electrical, magnetic, and optical properties
DOI		https://doi.org/10.1209/epl/i2006-10242-2
Published online		06 September 2006

Europhys. Lett., 76 (1), pp. 142-148 (2006)

Tuning the magnetic anisotropy of $\chem{Co}$ nanoparticles by metal capping

F. Luis¹, F. Bartolomé¹, F. Petroff²^,3, J. Bartolomé¹, L. M. García¹, C. Deranlot²^,3, H. Jaffrès²^,3, M. J. Martínez¹, P. Bencok⁴, F. Wilhelm⁴, A. Rogalev⁴ and N. B. Brookes⁴

¹ Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza and Departamento de Física de la Materia Condensada, Universidad de Zaragoza 50009 Zaragoza, Spain
² Unité Mixte de Physique CNRS/Thales - Route Départementale 128 91767 Palaiseau Cedex, France
³ Université Paris-Sud - 91405 Orsay Cedex, France
⁴ European Synchrotron Radiation Facility - BP 220, F-38043 Grenoble, France

Received: 31 March 2006
Accepted: 14 August 2006

Abstract

The magnetic anisotropy of Co clusters with diameters ranging from 1.1 $\un{nm}$ to 4.5 $\un{nm}$ turns out to be significantly larger than in bulk and strongly increasing with decreasing cluster size. The dominating role of the surface can be used to modify the anisotropy by changing the electronic properties of the matrix surrounding the clusters. We find that capping the clusters by a metallic (Cu and Au) layer significantly enhances the anisotropy, thus also stabilizing the magnetization against thermal fluctuations. The observed anisotropy enhancement is attributed to the bonding of the Co $3d$ electrons to the conduction band of the capping layer, which depends on the electronic band structures of both metals.

PACS: 75.50.Tt – Fine-particle systems; nanocrystalline materials / 75.70.-i – Magnetic properties of thin films, surfaces, and interfaces / 75.30.Gw – Magnetic anisotropy

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