Understanding the interaction of soft and hard magnetic components in NdFeB with first-order reversal curves

Sven Erik Ilse,Eberhard Goering,Gisela Schütz,Felix Groß,Joachim Gräfe

doi:10.1103/physrevb.103.024425

Sven Erik Ilse, Eberhard Goering + Show 3 more

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https://doi.org/10.1103/physrevb.103.024425

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Abstract

First-order reversal curve (FORC) measurements are a powerful tool to study magnetization reversal processes and interactions in heterogeneous systems with broad coercivity distributions. In NdFeB hard magnets an additional soft magnetic component is often observed possibly originating from damaged surface grains. Here we use FORC to study the reversal processes and interactions in these permanent magnets at different temperatures between 50 and 350 K. The measured reversal curves reveal a strongly coupled switching of the soft and hard magnetic components above 250 K. Below this temperature the two components are decoupled and switch almost independently. This decrease in effective interaction at lower temperatures is also observed in the FORC diagrams by a relative reduction in intensity of the so called interaction peak. This result proves that FORC is a powerful method, contributing to a better understanding of magnetization reversal processes and interactions in permanent magnets.

Highlights

First-order reversal curves (FORCs) can be utilized to study magnetic properties which are inaccessible for conventional magnetic characterization techniques
Since the demagnetizing factor depends on the geometry of the samples the shape of the hysteresis loop and the FORC density will change for different geometries
Room temperature FORC measurements with and without demagnetizing correction were compared. It appears that the samples interaction with its own stray field broadens the features in a FORC density along the Hu direction and shifts the soft magnetic peak in negative Hu direction

Summary

Introduction

First-order reversal curves (FORCs) can be utilized to study magnetic properties which are inaccessible for conventional magnetic characterization techniques. FORC, is able to provide more elaborate information such as coercive and interaction field distributions or interaction strength between interacting magnetic components [1,2]. Another advantage of FORC is that it can yield microstructural information about a system without the need of actual lateral resolution [2,3]. In 1986 Mayergoyz proposed to use first-order reversal curves as an experimental approach to the theoretical Preisach distribution.

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