Effect of interfacial and edge roughness on magnetoelectric control of Co/Ni microdisks on PMN-PT(011)

Y Hsiao,D B Gopman,P Shirazi,K Mohanchandra,C S Lynch

doi:10.1038/s41598-022-06285-6

Y Hsiao, D B Gopman + Show 3 more

Open Access

https://doi.org/10.1038/s41598-022-06285-6

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Journal: Scientific Reports	Publication Date: Mar 10, 2022
Citations: 1	License type: open-access

Affiliation: University of California, Los Angeles

Abstract

Uniform magnetic behavior within arrays of magnetoelectric heterostructures is important for the development of reliable strain-mediated microdevices. Multiple mechanisms may contribute to observed nonuniform magnetization reversal including surface roughness, non-uniform strain, and fabrication induced imperfections. Here, Co/Ni microdisks of 7 µm diameter were produced on both [Pb(Mg1/3Nb2/3)O3]1−x–[PbTiO3]x with x = 0.3 nominal composition (PMN-30PT) (011) and Si substrates, and the out-of-plane magnetization reversal was characterized using magneto-optical Kerr effect (MOKE). Coercivity variation across the microdisks within the arrays was observed on both the PMN-30PT and Si specimens with zero electric field applied. Co/Ni microdisks on a PMN-30PT substrate displayed relatively larger coercivity than those on a Si substrate due to the surface roughness effect. Quasistatic electric fields of varying magnitude were applied to the PMN-30PT substrate to assess the dependence of the coercivity on electric field induced strain. Our results indicate that while coercivity decreases with the increase of electric field induced strain, interfacial and edge roughness combine to realize a prohibitively large coercivity to overcome within the Co/Ni microdisks as well as a broad distribution of coercive field across a patterned microdisk array.

Highlights

Uniform magnetic behavior within arrays of magnetoelectric heterostructures is important for the development of reliable strain-mediated microdevices
The coercive field distribution was measured in an unstrained Co/Ni microdisk array grown on PMN-30PT and compared to an identical array grown on a smooth Si wafer to observe how the surface roughness affected the coercive field and the coercive field distribution across each array
Co/Ni microdisks were fabricated on PMN-30PT (011) and Si substrates and the effect of surface roughness, in-plane strain, and manufacturing defects were assessed. μ0HC variations across the Co/Ni microdisk arrays were observed on both the Si and PMN-30PT substrates with zero applied field, and the standard deviations of the μ0HC distribution were comparable for both arrays showing that surface roughness was not primary cause of the observed dispersion in μ0HC

Summary

Introduction

Uniform magnetic behavior within arrays of magnetoelectric heterostructures is important for the development of reliable strain-mediated microdevices. Multiple mechanisms may contribute to observed nonuniform magnetization reversal including surface roughness, non-uniform strain, and fabrication induced imperfections. Coercivity variation across the microdisks within the arrays was observed on both the PMN30PT and Si specimens with zero electric field applied. One recent study pointed to micrometer-scale variation in the strain generated from the FE PMN-PT substrate limiting the degree of uniform remagnetization behavior in an overlaid F M11. This inhomogeneous strain distribution may not be the only contribution to non-uniform behavior. Co/Ni microdisk heterostructures were patterned on PMN-30PT (011) and Si substrates to evaluate the magnetic coercive field and its variation across substrates and under strains from applied electric fields to the FE substrate. Application of an electric field was used to study the influence of strain on the coercive field response in the magnetostrictive Co/Ni heterostructures

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