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A B S T R A C T S WEDNESDAY, JUNE 30 N A N O S E A 2 0 1 0 Room Port-Pin 8H30-9h10 Metallic Alloys for high density recording media. D. Fiorani, G. Varvaro, S. Laureti, E. Agostinelli, A.M. Testa (ISM - CNR, Area ROMA 1, Via Salaria km 29.500, 00016 Roma, Italy ) dino.fiorani@ism.cnr.it 1 – Introduction Magnetic recording represents one of the most rapidly developing high technology areas. The computer hard disk drive has experienced an exponential increase in data capacity over time making it the predominant storage system for digital data [1]. This high growth rate has imposed more and more pressing requirements for the recording media and has driven the research and the development of new systems in order to get the better trade-off among three fundamental requirements (recording trilemma): thermal stability, medium signal-to-noise ratio and writability. 2 – Abstract The most promising materials (e.g. L10-Co(Fe)Pt films, [Co/Pd]n multilayers, CoCrPt@SO2 films), recording modes (e.g. perpendicular recording, thermally assisted writing), architectures (e.g. tilted and exchange spring media) and designs (e.g. patterned media) of recording media will be rewieved. The investigation, by using a vectorial VSM, of the magnetic properties of two different materials for perpendicular recording (tilted easy axis L10-CoPt(111)/Pt(111)/MgO(100) films and perpendicular easy axis [(Co90Cr10)80Pt20]92:(SiO2)8 media) will be reported. (111) oriented films of the L10-CoPt alloy have been deposited by using a conventional frontal Pulsed Laser Deposition. A very thin Pt (111) underlayer has been grown on MgO(100) and used to favour the epitaxial growth of the magnetic layer along the [111] direction, i.e. with the c-axis tilted at an angle of 36° with respect to the film plane. From the analysis of the angular dependence of the remanent magnetization, it has been found that the system presents 4 out-of-plane 36° easy axes with orthogonal in-plane projections. [(Co90Cr10)80Pt20]92@(SiO2)8 films have been grown by magnetron sputter deposition onto thermally oxidised Si wafers. A complex seed layer stack – Cr(5nm)/Ru(8nm)/Ru(12nm) – has been used to promote a perpendicular anisotropy. The experimental data indicate that both Stoner-Wohlfarth and Kondorsky reversal mechanism are present, with a predominance of the Kondorsky character with decreasing magnetic layer thickness. 3 – Conclusion The role of the metallic alloys in high density magneto-recording has been reported with particular emphasis on tilted easy axis L10-CoPt(111)/Pt(111)/MgO(100) films and perpendicular easy axis [(Co90Cr10)80Pt20]92:(SiO2)8 media. [1] H. J. Richter and A. Y. Dobin, J. Magn. Magn. Mater. 287, 41 (2005) 71
A B S T R A C T S WEDNESDAY, JUNE 30 N A N O S E A 2 0 1 0 9H10-9H30 Mechanism and compositions of GeMn self-assembled nanocolumns. LE THANH (1 Centre Interdisciplinaire de Nanoscience de Marseille (CINaM-CNRS), Aix-Marseille Université, Campus de Luminy, case 913, 13288 Marseille, France, 2 Department of Electronic Engineering, the University of Electro-Communications, 1-5-1 Chofugaoka, Chofu-shi, Tokyo 182-8585, Japan) 9H30-9H50 DMRG approach to molecular-based alternating spin bimetallic chains. DRZEWINSKI - P. Sobczak a , A. Barasiński b , R. Matysiak c , A. Drzewiński b , G. Kamieniarz a , J. Kłak d , A. Bieńko d , J. Mroziński d , D. Gatteschi e (aFaculty of Physics, A. Mickiewicz University, Poznań, Poland; bInstitute of Physics, University of Zielona Góra, Poland; cInstitute of Engineering and Computer Education, University of Zielona Góra, Poland; dDepartment of Chemistry, University of Wroclaw, Poland; dDepartment of Chemistry, University of Florence, Italy) 1 – Introduction Molecular magnets, including bimetallic chain systems, can be numerically analysed on the basis of the anisotropic quantum Heisenberg model [1]. To cover the entire experimental 1.7 − 300 K temperature range, the density-matrix renormalization group (DMRG) approach is very appealing. It has been exploited in the molecular nanomagnetism for the first time, analysing the experimental results for a number of compounds with the thiocyanate bridges without the mean-field corrections [1]. 2 – Abstract At first, a series of one-dimensional compounds comprising square planar tetraazamacrocycle copper(II) building blocks forming Cu(II)-SCN-M-NCS-Cu(II) chains, where M = Co, Ni, Mn, is reported. Although the thiocyanate ligands are weak magnetic mediators, both the ferromagnetic and antiferromagnetic interactions occur in our compounds and are not negligible [1]. The approach is applied also to the Re(IV) – Cu(II) complex [Cu(tren)]ReCl 6·2CH 3 OH, where both the exchange interaction J and the D zero-field splitting are expected to be much stronger [2]. The high accuracy results of our simulations have been fitted to the corresponding experimental susceptibility and magnetization data. To get an appropriate set of parameters, we always fitted both the magnetic susceptibility curves and the magnetization profiles to our numerical results. [1] A. Barasinski et al, Polyhedron (2010), doi: 10.1016/j.poly.2010.01.002 [2] A. Tomkiewicz, et al, Journal of Molecular Structure 644, 97 (2003) 3 – Conclusion For all the compounds, both the experimental susceptibility and field-dependent magnetization data have been fitted successfully using the quantum model without the mean-field corrections, leading to the sets of model parameters (the strength of magnetic couplings, the single-ion anisotropy terms and the corresponding g factors). The corresponding values for the Re(IV) – Cu(II) compound are the following: J/k B = 3.5 ± 0.5 K, D/k B = 35 ± 5 K, g Cu = 2.07 ± 0.05, g Re = 1.73 ± 0.01 72
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