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G13.9.1

Magnetic Domain Structures in CoNiFe Thin Films and Lines Lucas Pérez, Oscar de Abril, Claudio Aroca1, Pedro Sánchez1, Eloísa López and M.C. SánchezTrujillo Dpto. Física de Materiales, Universidad Complutense de Madrid, Ciudad Universitaria s/n Madrid, 28040, Spain. 1 ISOM and Dpto. Física Aplicada. ETSI Telecomunicación. Universidad Politécnica Madrid, 28040, Spain. ABSTRACT Thin films and arrays of lines of magnetic CoNiFe alloy have been produced by electrodeposition. A magnetic field was applied during the electrodeposition process in order to induce a magnetic anisotropy in the sample. The dependence of the magnetic properties and the magnetic domain structures on the thickness of the films is reported. In addition to this, the magnetic properties and the domain structure of a thin film and an array of lines, with the same thickness and deposited in the same conditions, have been compared. An increase in the coercivity of the array of lines has been shown. INTRODUCTION In the last few years there has been increased interest in electrodeposited CoNiFe alloys. These materials exhibit not only soft magnetic properties similar to NiFe but also higher saturation magnetization. They are therefore potential materials to replace NiFe alloys in the writing heads of magnetic recording systems as they would be able to achieve higher areal densities and higher data rates [1]. In the late nineties, many studies were published showing that, when plating under the appropriate conditions, CoNiFe alloys with coercivity below 1 Oe and saturation magnetization up to 2.1 T can be produced [2, 3]. In addition to high saturation magnetization and soft magnetic properties, high permeability at high frequency is also needed for magnetic recording heads. Magnetic properties at high frequency are influenced to a large extent by the micromagnetic domain structure of the films. Previous studies show the importance of the domain structure in the magnetic properties of these alloys [4, 5]. Almost every paper published until now is focused only on CoNiFe films thicker than 1 micron. To our knowledge, there are only three papers [4, 6, 7] which address magnetic properties of thinner films, but none dealing with magnetic properties of micro-lines of CoNiFe alloys. In this work the magnetic properties and the domain structure of thin films and micro-lines of CoNiFe alloys ranging from 125 nm to 1 µm thickness are presented. EXPERIMENTAL DETAILS CoNiFe thin films and lines were fabricated by means of electrochemical deposition under current control conditions. Electrodeposition was carried out at room temperature, in a Pyrex cell with vertical, parallel, stationary electrodes. Si / Ti (30nm) / Cu (120 nm) substrates with a squared masked area of 1 cm2 were used for the deposition of the thin films. For the

G13.9.2

electrodeposition of lines, a pattern on the substrate was defined by UV-lithography. The lines had a width of 100 µm and a length of 5 mm with a distance between them of 100 µm. To induce a magnetic anisotropy, a magnetic