Size Dependent Enhancement of Spin and Orbital Magnetism in CoRh Nanoparticles
- PDF / 169,384 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 101 Downloads / 139 Views
0998-J01-02
Size Dependent Enhancement of Spin and Orbital Magnetism in CoRh Nanoparticles M. MuÒoz-Navia1,2, J. Dorantes-D·vila2, C. Amiens3, B. Chaudret3, D. Zitoun3, M.-J. Casanove4, P. Lecante4, N. Jaouen5, A. Rogalev5, M. Respaud6, and G. M. Pastor7 1 Max-Planck-Institut f¸r Mikrostrukturphysik, Halle, D-06120, Germany 2 Instituto de FÌsica, Universidad AutÛnoma de San Luis PotosÌ, San Luis PotosÌ, 78000, Mexico 3 Laboratoire de Chimie de Coordination, CNRS, Toulouse, 31077, France 4 Centre d'Elaboration de MatÈriaux et d'Etudes Structurales, CNRS, Toulouse, 31077, France 5 European Synchrotron Radiation Facility, Grenoble, 38043, France 6 Laboratoire de Physique et Chimie des Nano-objets, INSA, Toulouse, 31077, France 7 Institut f¸r Theoretische Physik, Universit‰t Kassel, Heinrich Plett Str. 40, Kassel, D-34132, Germany ABSTRACT The magnetism of CoRh nanoparticles (NPs) is investigated experimentally and theoretically. NPs of about 2 nm diameter have been synthesized by decomposition of organometallic precursors in mild conditions of pressure and temperature, under hydrogen atmosphere and in the presence of a polymer matrix. The magnetic properties are determined by SQUID and X-ray magnetic circular dichroism. All the studied CoRh clusters are magnetic with an average spin moment per atom that is significantly larger than the one of macroscopic crystals or alloys with similar concentrations. The experimental results and the comparison with theory suggest that the most likely chemical arrangement is a Rh core with a Co-rich outer shell and some degree of intermixing at the CoRh interface. A detailed analysis of the theoretical results from a local perspective shows that the spin and orbital moments of the Co and Rh atoms at the interface are largely responsible for the enhancement of the magnetization. INTRODUCTION The magnetism in monometallic ferromagnetic (FM) 3d transition-metal (TM) nanoparticles (NPs) containing less than 1000 atoms has been the subject of numerous experimental and theoretical studies. It is nowadays relatively well understood that the large surface-to-volume ratio induces an enhancement of the spin and orbital magnetic moments and of the magnetic anisotropy energy (MAE) as compared to the bulk materials.1,2 In contrast very little is still known about the behaviour of magnetic nanoalloys. This subject is currently attracting considerable attention both from fundamental and technological perspectives. For example, for material science applications one would like to be able to develop magnetic NPs that combine both high saturation magnetization (MS) and large MAE. This can indeed be achieved by starting from a FM 3d metal and by associating it with a second heavier element that displays a stronger spin-obit coupling and a potentially significant contribution to the total magnetization. Quite generally, 4d and 5d metals appear as very good candidates for this purpose. CoRh clusters are particularly appealing since Rh shows non-saturated ferromagnetism in small clusters despite being non-m
Data Loading...
