June 2007 EPL, 78 (2007) 67004 www.epljournal.org doi: 10.1209/0295-5075/78/67004 Magnetostatic interactions between two magnetic wires R. Piccin 1,2 , D. Laroze 3,4 , M. Knobel 2 , P. Vargas 5,6 and M. V´ azquez 7 1 Dipartimento di Chimica IFM and NIS, Universit` a di Torino - Via P. Giuria 9, 10125, Torino Italy 2 Instituto de F´ısica Gleb Wataghin (IFGW), Universidade Estadual de Campinas - UNICAMP, C.P. 6165, Campinas 13083-970 SP, Brazil 3 Instituto de F´ısica, Universidad Cat´ olica de Valpara´ıso - Casilla 4059, Valpara´ıso, Chile 4 Departamento de F´ısica, Facultad de Ciencias F´ısicas y Matem´ aticas, Universidad de Chile - Casilla 487-3, Santiago, Chile 5 Departamento de F´ısica, Universidad T´ecnica Federico Santa Mar´ıa - Casilla 110V, Valpara´ıso, Chile 6 Max-Planck-Institute for Solid State Research - Heisenbergstrasse 1, D-70569 Stuttgart, Germany 7 Instituto de Ciencias de Materiales de Madrid, CSIC - Campus Cantoblanco, 28049 Madrid, Spain received 26 January 2007; accepted in final form 3 May 2007 published online 29 May 2007 PACS 75.50.Kj – Amorphous and quasicrystalline magnetic materials PACS 75.60.-d – Domain effects, magnetization curves, and hysteresis PACS 75.50.-y – Studies of specific magnetic materials Abstract – The results of the magnetic dipolar field in a simple set of two amorphous ferromagnetic wires of composition Fe77.5Si12.5B15 placed side by side are presented. Owing to their peculiar domain structure, they could, in principle, be approximated by macroscopic magnetic dipoles, allowing the analysis of the magnetostatic field between these magnetic entities. Magnetization measurements as a function of the distance between the parallel wires were performed. Results can be explained considering the magnetostatic field created by one wire in the neighboring one. It is clearly shown that this field is responsible for changes of the reversal field of the wires, leading to the appearance of plateaux during the demagnetization process. Instead of pure dipolar model that does not fit experimental data, a multipolar model has been developed, showing a rather good agreement with the experimental results. Copyright c  EPLA, 2007 Introduction. – Dipolar interactions among magnetic entities have been widely studied, because they are fundamental to the progress of basic research and to the development of a number of application oriented novel magnetic devices. Advances in fabrication techniques (including chemical routes, electrodeposition and litho- graphy) have allowed the fabrication of nanostructured systems with very interesting physical properties. In particular, it is nowadays possible to obtain controlled arrays of magnetic wires with diameters of few nano- meters, which are of practical interest in the design and optimization of devices for ultrahigh-density data storage applications, for example [1]. In such systems, as in many other artificial magnetic structures, magnetostatic inter- actions may play a fundamental role in the magnetization reversal process and domain structures of the individual elements, which consequently would influence the overall magnetic response of the system. The magnetic dipole is the basic entity of magnetism. Any calculation or simulation used to describe the magnetic behavior of a system employs this concept. However, in the case of real systems, either nano, micro or macroscopic, the effective magnetostatic interactions among the elements are still unknown, although they could have a strong influence on the macroscopic magnetic behaviour of the system. An intrinsic obstacle in the experimental study of magnetic interactions is the fact that it is extremely difficult to single out an individual magnetic element, even using the most sensitive magne- tometric techniques. Also, the predictions of numerical simulations are intricate to compare with real systems, owing to the necessity of introducing several approxima- tions in the modeled problem. However, a very interesting macroscopic analogous has been extensively studied, placing together several ferromagnetic amorphous wires and microwires [2]. The stray fields couple the magneti- zations of neighboring wires, affecting the magnetic state of each single wire. Such systems are relatively easy to study experimentally, and, in the case of few wires, it was possible to obtain analytical solutions (by assuming a 67004-p1