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Surface effect on atomic ordering in nano-layered L1₀ AB binaries: multiscale Monte Carlo Simulation

Rafal Kozubski ¹, Mirosław Kozłowski ¹, Jan Wróbel ², Tomasz Wejrzanowski ^3,4, Krzysztof J. Kurzydlowski ³, Christine Goyhenex ⁵, Véronique Pierron-Bohnes ⁵, Marcus Rennhofer ⁶, Savko Malinov ⁷

1. Jagiellonian University, Institute of Physics (IF UJ), Reymonta 4, Kraków 30-059, Poland
2. Warsaw University of Technology, Faculty of Physics, Koszykowa 75, Warszawa 00-662, Poland
3. Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland
4. Interdisciplinary Centre for Materials Modelling (ICMM), Woloska 141, Warszawa 02-507, Poland
5. Institut de Physique et Chimie des Materiaux de Strasbourg, UMR7504, CNRS - ULP, 23, rue du Loess, BP 43, Strasbourg CEDEX 2 67034, France
6. University of Vienna, Institute of Materials Physics, Wien, Austria
7. Queen's University Belfast (QUB), Stranmillis Road, Belfast BT9 5AH, United Kingdom

Abstract

Combined nano- and mesoscale simulation of chemical ordering kinetics in nano-layered L1₀ AB binary intermetallics was performed. In the nano- (atomistic) scale Monte Carlo (MC) technique implemented with vacancy mechanism of atomic migration and diverse models for the system energetics were used. The meso-scale microstructure evolution was, in turn, modelled by means of a Monte Carlo procedure simulating antiphase-domain-boundary motion as controlled by antiphase-boundary energies evaluated within the nano-scale simulations. The study addressed FePt thin layers considered as a material for ultra-high-density magnetic storage media and revealed metastability of the L1₀ c-variant superstructure with monoatomic planes parallel to the layer surface and off-plane easy magnetization. The layers, originally perfectly ordered in a c-variant of the L1₀ superstructure, showed homogeneous disordering running in parallel with a spontaneous re-orientation of the monoatomic planes leading to a mosaic microstructure composed of a- and b-L1₀-variant domains. The domains nucleated heterogeneously on the free surface of the layer and grew discontinuously inwards its volume. Finally, the domains relaxed towards an equilibrium microstructure of the system. Two “atomistic-scale” processes: (i) homogeneous disordering and (ii) nucleation of the a- and b-L1₀-variant domains showed characteristic time scales. The same was observed for the meso-scale processes: (i) heterogeneous L1₀-variant domain growth and (ii) domain microstructure relaxation. The above complex structural evolution modelled by means of the multiscale Monte Carlo simulations has recently been observed experimentally in epitaxially deposited thin films of FePt [1].

[1] M. Rennhofer, B. Sepiol, G. Vogl, M. Kozlowski, R. Kozubski, B. Laenens, A. Vantomme, J. Meersschaut, Diffusion Fundamentals 6 (2007) 45.1 - 45.2

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Surface effect on atomic ordering in nano-layered L10 AB binaries: multiscale Monte Carlo Simulation

Presentation: Oral at E-MRS Fall Meeting 2008, Symposium G, by Rafal Kozubski See On-line Journal of E-MRS Fall Meeting 2008 Submitted: 2008-05-09 13:05 Revised: 2009-06-07 00:48

Surface effect on atomic ordering in nano-layered L1₀ AB binaries: multiscale Monte Carlo Simulation

Presentation: Oral at E-MRS Fall Meeting 2008, Symposium G, by Rafal Kozubski
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-09 13:05 Revised: 2009-06-07 00:48