Influence of the Distance between Nanoparticles in Clusters on the Magnetization Reversal Process

Andrea Ehrmann,Tomasz Blachowicz

doi:10.1155/2017/5046076

Andrea Ehrmann, Tomasz Blachowicz

Open Access

https://doi.org/10.1155/2017/5046076

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Abstract

Fourfold magnetic nanoparticles, created from nanowires or in the form of an open square, offer the possibility of creating quaternary memory devices with four unambiguously distinguishable stable states at remanence. This feature, however, has been simulated for single magnetic nanoparticles or clusters with interparticle distances similar to the nanoparticle dimensions. For the possible use in bit-patterned media, it is important to understand the scaling behavior of the stability of the additional intermediate states with the interparticle distance. The paper investigates exemplarily nanoparticles of two shapes which were found to be optimum to gain four states at remanence. For clusters of these particles, the probability of reaching the additional intermediate states in all particles in the same field region is strongly reduced with decreased interparticle distance. The differences between both shapes indicate possible solutions for this problem in the form of new nanoparticle shapes.

Highlights

Magnetic nanoparticles are of technological interest, for example, for magnetic storage media, magnetic sensors, and MRAMs [1,2,3]
While the hysteresis loops for the single particle and for the 4 × 4 cluster with interparticle distances half of the particle diameters are nearly identical, the cluster with interparticle distances of only a quarter of the particle diameters results in a significantly modified hysteresis loop
The simulated clusters were modified with respect to their interparticle distances in a range between half the particle dimension and 1/8 of the particle dimension

Summary

Introduction

Magnetic nanoparticles are of technological interest, for example, for magnetic storage media, magnetic sensors, and MRAMs [1,2,3] Since their overall anisotropy is governed by the shape anisotropy [4], tailoring a nanoparticle’s form allows for adjusting its magnetic properties. One possible shape consists of a fourfold ring with different shape modifications, leading to two additional magnetic states at remanence which could be used to create quaternary memory systems [5]. In this way, data storage density could be increased by increasing the number of bits per particle instead of increasing the particle density. This approach has been followed by other groups, resulting in three, four, or up to eight magnetization states in diverse nanostructures [6,7,8,9,10]

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