Analysis Interaction Field Strength and Spectrum from Microhysteresis Loops
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0998-J08-17
Analysis Interaction Field Strength and Spectrum from Microhysteresis Loops Lin-Xiu Ye, Jia-Mou Lee, and Te-ho Wu Graduate school of Engineering Science & Technology and Taiwan SPIN Research Center, Nat'l Yunlin Univ. of Science and Technology, 123 University Road, Section 3, Douliou, Yunlin, 64002, Taiwan
ABSTRACT In this paper, we present a direct method to analyze the mechanism of magnetic domain reversal for a series of amorphous Dyx(FeCo)1-x magnetic thin films and whereby we obtained the distributions of the coercivities and interaction fields from 90,000 measurements of the microhysteresis loops. The standard deviations of the coercivity and the interaction field distributions, σi and σk, can be estimated by fitting the experimental data with the GaussianPreisach function. The results show that the interaction field decreases as Dy composition approaches the compensation point. The reversal mechanism is dominated by nucleation when σi is smaller than σk. The relationships between the magnetization reversal and interaction field strength are discussed. INTRODUCTION The contribution of interaction fields in various domain reversal processes has been studied by using the micro-hysteresis loop method [1]. The mechanism and dynamics of the domain reversal process [2] are important both from the fundamental physics - and application viewpoints for perpendicular magnetic thin films. Hysteresis loop measurement [3] is one of the major ways to characterize the domain reversal processes of magnetic materials. For example, many researchers use the first order reversal curves (FORC) diagram to get the Preisach distribution [4]. However, the FORC diagram method is an indirect method to obtain the statistical distribution of the interaction field, assuming the material as a collection of squareloop hysterons. Each FORC is measured by saturating the sample, decreasing the field to a value HA, and reversing the field sweeping to the saturated state in a series of field steps (HB). This process is then repeated many times to obtain a series of values of HA. The magnetizations M(HA,HB) measured at each step and the mixed second derivatives are taken to create the FORC distribution [5]. Contrarily, the method demonstrated in present paper on the samples of a series of amorphous Dyx (FeCo) 1-x magnetic thin films - based on microhysteresis loop measurements by Kerr microscope, is a direct way to analyze the interaction field strength and spectrum of the coercivities and thus obtain the Preisach distribution. Furthermore, the dominating reversal mechanism for magnetic domain reversal can be determined by comparing the standard deviations of the coercivity and the interaction field distributions. EXPERIMENTS A series of amorphous Dyx(FeCo)1-x magnetic thin films were fabricated by DC magnetron co-sputtering. To measure the microhysteresis loops we used the Kerr microscope equipped with an electromagnet capable of producing a 5 kOe magnetic field and a CCD camera with a resolution of 300k pixels to grab continuous dom
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