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Lecture Tristan Cren


24 January 2005 FWN-Building 5113.0202, Nijenborgh 4, 9747 AG, Groningen
Speaker: Dr. Tristan Cren
Affiliation: Institute of the Physics of Nanostructures EPFL, Switzerland and Groupe de Physique des Solides, CNRS, Université Paris VI, France
Title: Magnetic anisotropy of nanostructures at surfaces
Date: Mon Jan 24, 2005
Start: 14.00
Location: FWN-Building 5113.0202
Host: P. Rudolf
Telephone: +31 50 363 4736 / 4974 (secr.)


The magnetic anisotropy energy K is one of the key quantities in the design of novel magnetic recording media, as it defines the stability of the magnetization direction against thermal fluctuations and therefore the so-called superparamagnetic density limit where magnetic information becomes volatile. Using Magneto-optical Kerr effect (MOKE) we investigate the magnetic properties of 2D nanostructures in-situ to their MBE growth at surfaces. A one-to-one comparison of the magnetism of the particle ensemble with their morphology determined with STM enables us to identify the contribution of the differently coordinated atoms. We find spectacular magnetic properties for low coordinated atoms at surfaces. For Co/Pt(111) we find that edge atoms have 20 times the Cohcp bulk anisotropy and favor out-of-plane magnetization. This result is corroborated by XMCD measurements, where we follow the evolution of K as a function of size almost atom by atom.

Currently, the best homogeneity of magnetic properties is obtained for Co islands self-assembled on Au(778). We show the absence of mutual interactions for this case. With a density of 26 Tera in-2, and the narrow K-distribution Co/Au(788) presents a model system for exploring the ultimate density limits of magnetic information storage. We finally show our attempts to image the individual magnetization directions with spin polarized STM and we discuss first results obtained on bi-metallic islands.

Last modified:22 October 2012 2.30 p.m.