Abstract
We report observation of a radial dependence in the magnetic anisotropy of epitaxially strained CoFe2O4 nanopillars 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. The anisotropy originates from the large magnetostriction of CoFe2O4 and the state of stress within the nanocomposite. Magnetometry suggests the existence of two magnetic phases with different anisotropies. Micromagnetic simulations of a core-shell magnetic anisotropy qualitatively reproduce features of the magnetic hysteresis and elucidate the magnetization reversal mechanism: The magnetization initially reorients within the pillar core, followed by that of the shell. This is consistent with polarized small-angle neutron scattering which can be described by a CoFe2O4 magnetization that is nonuniform on nanometer length scales. As the length scale of inhomogeneity of the magnetic anisotropy is similar to estimates of the relaxation of the displacement field from the CoFe2O4-BaTiO3 interface, stress and its influence on structure provide an important route to new functionality of vertically aligned nanopillars for applications in low-power memory, computing, and sensing.
| Original language | English |
|---|---|
| Article number | 081401 |
| Journal | Physical Review Materials |
| Volume | 3 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 1 2019 |
Funding
The experimental of assistance of Dr. J. R. Krzywon is gratefully acknowledged. Discussions with Professor Cevdet Noyan are gratefully acknowledged. This work was supported by the U.S. Department of Energy (DOE), Office of Science (OS), Basic Energy Sciences (BES), Materials Sciences and Engineering Division (sample design, fabrication, and physical property characterizations) and by the Laboratory Directed Research and Development (LDRD) Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. DOE. The research at ORNL's Spallation Neutron Source and High Flux Isotope Reactor was sponsored by the Scientific User Facilities Division, BES, U.S. DOE. We acknowledge the support of the National Institute of Standards and Technology, U.S. Department of Commerce, in providing the neutron research facilities used in this work. This work utilized facilities supported in part by the National Science Foundation under Agreement No. DMR-1508249. The work at Los Alamos National Laboratory was supported by the NNSA's Laboratory Directed Research and Development Program and was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy Office of Science. Los Alamos National Laboratory, an affirmative action equal opportunity employer, is managed by Triad National Security, LLC, for the U.S. Department of Energy’s NNSA, under Contract No. 89233218CNA000001. This work benefited from the use of the sasview application, originally developed under NSF Award No. DMR-0520547. sasview contains code developed with funding from the European Union's Horizon 2020 research and innovation program under the SINE2020 project, Grant Agreement No. 654000.