Nanoscale Magnetization Inhomogeneity within Single Phase Nanopillars

Published

August 1, 2019

Author(s)

Thomas O. Farmer, Er-Jia Guo, Ryan D. Desautels, Lisa Debeer-Schmitt, Aiping Chen, Zhongchang Wang, Quanxi Jia, Julie Borchers, Dustin A. Gilbert, Ben Holladay, Sunil K. Sinha, Michael R. Fitzsimmons

Abstract

We report observation of a radial dependence in the magnetic anisotropy of epitaxially strained CoFe₂O₄ nanostructures in a BaTiO₃ matrix. This archetypal example of a multiferroic heterostructure with a self-assembling three dimensional architecture possesses significant out-of-plane uniaxial magnetic anisotropy, which originates from the large magnetostriction of CoFe₂O₄ and the particular strain state in the nanocomposite. Magnetic measurements suggest the existence of two magnetic phases with different anisotropies. Micromagnetic simulations of a core-shell magnetic anisotropy have replicated the essential features of the magnetic hysteresis loops and elucidated the magnetization reversal mechanism: the magnetization initially reorients within the pillar core, eventually followed by the shell. This is consistent with polarized small angle neutron scattering which can be described by a CoFe₂O₄ magnetization that is non-uniform on nanometer length scales. As the inhomogeneity in the magnetic anisotropy appears to occur due to strain relaxation away from the CoFe₂O₄-BaTiO₃ interface, it should be influential in all similar structures with a magnetostrictive component. This provides an important route to new functionality in vertically aligned nanostructures for applications in low-power memory and computing, possibly enabling an alternative approach to neuromorphic computing strategies.

Citation

Physical Review Materials

Volume

3

Issue

8

Pub Type

Journals

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Keywords

Magnetic nanopillars, Micromagnetic simulation, Small angle neutron scattering, Core shell behavior

Citation

Farmer, T. , Guo, E. , Desautels, R. , Debeer-Schmitt, L. , Chen, A. , Wang, Z. , Jia, Q. , Borchers, J. , Gilbert, D. , Holladay, B. , Sinha, S. and Fitzsimmons, M. (2019), Nanoscale Magnetization Inhomogeneity within Single Phase Nanopillars, Physical Review Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=926013 (Accessed April 17, 2024)