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Nanoscale Magnetization Inhomogeneity within Single Phase Nanopillars

Published

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

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 March 4, 2024)
Created July 31, 2019, Updated October 12, 2021