Controlling the Magnetic Structure of CoNi Microparticles by Mechanical Stress
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Controlling the Magnetic Structure of CoNi Microparticles by Mechanical Stress N. I. Nurgazizova, *, D. A. Bizyaeva, A. A. Bukharaeva, and A. P. Chuklanova a Zavoisky
Kazan Physico-Technical Institute, FRC Kazan Scientific Center, Russian Academy of Sciences, Kazan, 420011 Russia *e-mail: [email protected] Received March 26, 2020; revised March 26, 2020; accepted April 2, 2020
Abstract—The changes in the domain structure of CoNi microparticles under action of mechanical stresses have been studied. With this purpose, an array of identical planar square CoNi particles has been formed on the surface of a polished glass substrate. An elastic bending of the substrate has been used to induce mechanical stresses in the particles. It is shown, using magnetic-force microscopy, that the magnetic structure of the particles can be changed from the multidomain to quasi-homogeneous magnetization using mechanical stresses. Keywords: planar magnetic microparticles, magnetic-force microscopy, magnetoelastic effect DOI: 10.1134/S106378342009022X
1. INTRODUCTION The magnetoelastic effect (the Villary effect) or the influence of mechanical stresses on the magnetic properties of ferromagnetic materials can be used for controlling the magnetization of micro- and nanoparticles [1–4]. The interest in such a method of controlling the magnetization is related to the fact that such an approach can substantially decrease the total energy consumptions necessary to change the direction of the magnetization of a single-domain particle. Based on such particles, low-energy devices for processing and storing information can be designed [2, 3]. The magnetic-force microscopy is the most promising method of studying the magnetic structure and the process of magnetization switching of an individual particle or a small array of particles. The magneticforce microscope (MFM) makes it possible to study the magnetic structure at various external conditions with a high spatial resolution (to 10 nm). In some cases, using microparticles of a certain shape, we can solve also the inverse problem of determination of mechanical stresses acting on a particle based on an analysis of its magnetic structure [4, 5]. To visualize mechanical stresses in a near-surface layer, not only particle but also continuous films can be used [6, 7], but in practice the MFM is not suitable for studying thin films. In this work, the influence of a mechanical stress on the magnetic structure of planar CoNi microparticles of square shape was studied. Earlier it was shown for permalloy (Py) microparticles that the square shape particles can be used to determine the directions
of a uniaxial mechanic stress and also to estimate its value. However, to change the magnetic structure of Py particles with lateral sizes 7.5 μm, very high mechanical stress are necessary which cannot be experimentally achieved without destruction the sample. Thus, in this work, we studied the particles prepared from CoNi alloy that has a much higher constant of the saturation magnetostriction (λs = –25 × 10–6
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