| AVS 58th Annual International Symposium and Exhibition | |
| Magnetic Interfaces and Nanostructures Division | Wednesday Sessions |
| Session MI-WeM |
| Session: | Fundamental Problems in Magnetism |
| Presenter: | Cyril Chacon, Lab. Mat. et Phénomènes Quantiques, France |
| Authors: | P. Campigilo, Lab. Mat. et Phénomènes Quantiques, France N. Moreau, Lab. Mat. et Phénomènes Quantiques, France V. Repain, Lab. Mat. et Phénomènes Quantiques, France C. Chacon, Lab. Mat. et Phénomènes Quantiques, France H. Bulou, Inst. de Phys. et Chimie des Mat. de Strasbourg, France F. Scheurer, Inst. de Phys. et Chimie des Mat. de Strasbourg, France P. Ohresser, Synchrotron SOLEIL, France H. Magnan, Service de Phy. et Chimie des Surfaces et Interfaces, France E. Fonda, Synchrotron SOLEIL, France J. Lagoute, Lab. Mat. et Phénomènes Quantiques, France Y. Girard, Lab. Mat. et Phénomènes Quantiques, France C. Goyhenex, Inst. de Phys. et Chimie des Matériaux de Strasbourg, France S. Rousset, Lab. Mat. et Phénomènes Quantiques, France |
| Correspondent: | Click to Email |
Core-shell nanoparticles have been receiving an increasing attention in order to practically employ magnetic clusters in devices [1]. The shell permits to protect the magnetism of the core, which readily oxidize in environmental conditions. Moreover, the shell can donate to the particle new chemico-physical functionalities which, combined with magnetism, permit to obtain multifunctional systems. Cobalt self-organized supported nanodots are promising candidates for applications as very high density magnetic recording media. However, it is necessary to improve the magnetic stability of such small nanostructures against thermal excitations. The capping with a non-magnetic metal of magnetic nanostructures induces different interfacial phenomena which together lead to a modification of the magnetic behavior of the system.
In the present work, the growth and the magnetism of Co/Pt core-shell have been studied. Pt has been deposited as over layer on Co self-organized on Au(111) template. The structural properties have been addressed by combining Scanning Tunneling Microscopy (STM) and Surface Extended X-ray Absorption Fine Structure (SEXAFS) measurements with molecular dynamics calculations. Magneto-Optic Kerr Effect (MOKE) and X-ray Magnetic Circular Dichroism (XMCD) have been coupled in order to identify the main magnetic phenomena acting at the Co/Pt interface. In the submonolayer regime, Pt forms metal rims around Co nanodots, and the Co magnetic anisotropy decreases. On the other hand, if more than one monolayer of Pt is deposited, the Co dots are completely covered and their magnetic anisotropy is enhanced. Furthermore, the Pt capping is found to have a minor effect of the cobalt magnetic moments. By changing the deposition conditions and by comparing the effect of Pt and Au capping [2], we identified three principal phenomena at the Co/Pt interface: inter-mixing, magnetoelasticity and band hybridization. Our results indicate that the principal one is band hybridization, which is responsible for the observed increasing of magnetic anisotropy. Intermixing and magnetoelasticity have rather the opposite effect and tend to decrease the magnetic anisotropy energy. The knowledge of the interplay between these different phenomena is fundamental in order to tune the magnetic properties of nanoparticles for precise applications, from data storage to biomedical research.
[1]A. Lu, E. Salabas, and F. Schüth, Angew. Chem. Int. Ed. 46, (2007) 1222.
[2] Y. Nahas, V. Repain, C. Chacon, Y. Girard, J. Lagoute, G. Rodary, J. Klein, S. Rousset, H. Bulou, and C. Goyhenex, Phys. Rev. Lett., 103 (2009) 067202.