J Comput Electron (2008) 7: 454–457 DOI 10.1007/s10825-007-0157-3 Field-coupled computing in magnetic multilayers György Csaba · Paolo Lugli · Markus Becherer · Doris Schmitt-Landsiedel · Wolfgang Porod Published online: 12 December 2007 © Springer Science+Business Media LLC 2007 Abstract This paper presents a computational study of ion- beam patterned cobalt-platinum multilayers, which could be used for field-coupled computing. We use micromagnetic simulations to reproduce measured hysteresis curves. This parameterized micromagnetic simulator then will be used for simulating interacting magnetic dots. We demonstrate how logic gates can be built from such coupled dots. We also show how electrical wires—placed beneath or above the magnetic dots—can provide a magnetic field, which propa- gates the magnetic signals. Keywords Magnetic logic devices · Field-coupled computing · Micromagnetic simulation · Cobalt/platinum multilayers · FIB patterning · Clocking of field-coupled devices 1 Introduction Magnetic field-coupling (also known as Magnetic Quantum- dot Cellular Automata, M-QCA) is an emerging paradigm G. Csaba ( ) · P. Lugli Institute for Nanoelectronics, Technical University of Munich, 80333 Munich, Germany e-mail: csaba@tum.de M. Becherer · D. Schmitt-Landsiedel Institute for Technical Electronics, Technical University of Munich, 80333 Munich, Germany D. Schmitt-Landsiedel e-mail: dsl@tum.de W. Porod Center for Nano Science and Technology, University of Notre Dame, Notre Dame, IN 46556, USA e-mail: porod@nd.edu of nanoscale computing, where information is propagated and processed by the dipole interaction of single-domain magnetic particles [1]. The feasibility of this concept has recently been demonstrated experimentally by a magnetic majority gate, fabricated from Permalloy dots [2]. We have shown theoretically that magnetic field-coupled circuits can achieve fast and densely integrated computing which dissipates only few kT power per switching [3, 4]. Additionally, field-pumped magnetic logic devices show power gain. Overall, magnetic logic devices are functionally equivalent to transistor-based circuits and in some applica- tions (which are storage-intensive, require low power, etc.), they can substitute or complement CMOS-based circuitry. Magnetic logic devices so far have been fabricated by lift- off, following electron-beam lithography [2]. Such nano- magnets show relatively large switching field variations from dot to dot. It turned out to be challenging to realize a larger-scale magnetic computing device as the dot to dot variations of magnetic properties frustrates magnetic order- ing and hinders the propagation of magnetic signals. Cobalt-platinum multilayers were a subject of extensive research in the past decades [5]. They show perpendicular magnetic anisotropy (PMA, i.e. their magnetization prefers an out of plane orientation) and they can be patterned into dots by focused ion beams (FIB) without actually remov- ing material from the surface. The PMA is advantageous for field-coupled architectures [6] and FIB patterning produces dots which show well-defined magnetic properties. The goal of this paper is to use micromagnetic simula- tions to asses the feasibility of a field-coupled computing device based on FIB-defined nanomagnets. The next section briefly describes the structures we fabricated and introduces the simulation framework. In Sect. 3 we show, how a stan- dard micromagnetic simulation code (OOMMF) can be pa- rameterized for the simulation of magnetic multilayers. Sim-