skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Strain induced anisotropy in liquid phase epitaxy grown nickel ferrite on magnesium gallate substrates
Abstract This work focuses on the nature of magnetic anisotropy in 2.5–16 micron thick films of nickel ferrite (NFO) grown by liquid phase epitaxy (LPE). The technique, ideal for rapid growth of epitaxial oxide films, was utilized for films on (100) and (110) substrates of magnesium gallate (MGO). The motivation was to investigate the dependence of the growth induced anisotropy field on film thickness since submicron films of NFO were reported to show a very high anisotropy. The films grown at 850–875 C and subsequently annealed at 1000 C were found to be epitaxial, with the out-of-plane lattice constant showing unanticipated decrease with increasing film thickness and the estimated in-plane lattice constant increasing with the film thickness. The uniaxial anisotropy field H σ , estimated from X-ray diffraction data, ranged from 2.8–7.7 kOe with the films on (100) MGO having a higher H σ value than for the films on (110) MGO. Ferromagnetic resonance (FMR) measurements for in-plane and out-of-plane static magnetic field were utilized to determine both the magnetocrystalline the anisotropy field H 4 and the uniaxial anisotropy field H a . Values of H 4 range from −0.24 to −0.86 kOe. The uniaxial anisotropy field H a was an order of magnitude smaller than H σ and it decreased with increasing film thickness for NFO films on (100) MGO, but H a increased with film thickness for films on (110) MGO substrates. These observations indicate that the origin of the induced anisotropy could be attributed to several factors including (i) strain due to mismatch in the film-substrate lattice constants, (ii) possible variations in the bond lengths and bond angles in NFO during the growth process, and (iii) the strain arising from mismatch in the thermal expansion coefficients of the film and the substrate due to the high growth and annealing temperatures involved in the LPE technique. The LPE films of NFO on MGO substrates studied in this work are of interest for use in high frequency devices.  more » « less
Award ID(s):
1808892 1923732
PAR ID:
10339064
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ;
Date Published:
Journal Name:
Scientific Reports
Volume:
12
Issue:
1
ISSN:
2045-2322
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; (, Journal of Composites Science)
    This report is on the nature of strain in thin films of yttrium iron garnet (YIG) on yttrium aluminum garnet (YAG) substrates due to film-substrate lattice mismatch and the resulting induced magnetic anisotropy. Films with thickness 55 nm to 380 nm were deposited on (100), (110), and (111) YAG substrates using pulsed laser deposition (PLD) techniques and characterized by structural and magnetic characterization techniques. The in-plane strain determined to be compressive using X-ray diffraction (XRD). It varied from −0.12% to −0.98% and increased in magnitude with increasing film thickness and was relatively large in films on (100) YAG. The out-of-plane strain was tensile and also increased with increasing film thickness. The estimated strain-induced magnetic anisotropy field, found from XRD data, was out of plane; its value increased with film thickness and ranged from 0.47 kOe to 3.96 kOe. Ferromagnetic resonance (FMR) measurements at 5 to 21 GHz also revealed the presence of a perpendicular magnetic anisotropy that decreased with increasing film thickness and its values were smaller than values obtained from XRD data. The PLD YIG films on YAG substrates exhibiting a perpendicular anisotropy field have the potential for use in self-biased sensors and high-frequency devices. 
    more » « less
  2. ; ; ; ; ; ; (, Journal of Vacuum Science & Technology A)
    We report on the x-ray absorption spectra (XAS) and x-ray magnetic circular dichroism (XMCD) of a series of NiFe2O4 (Ni ferrite) films grown on symmetry matched substrates and measured in two geometries: out-of-plane and near in-plane. The Ni ferrite films, grown by pulsed laser deposition, are epitaxial and the substrates used (ZnGa2O4, CoGa2O4, MgGa2O4, and MgAl2O4) introduce a systematic variation in the lattice mismatch between the substrate and the film. Modeling of the XAS and XMCD spectra, both measured with the surface sensitive total electron yield mode, indicates that the Ni2+ cations reside on the octahedrally coordinated lattice sites in the spinel structure. Analyses of the Fe XAS and XMCD spectra are consistent with Fe3+ cations occupying a subset of the octahedral and tetrahedral sites in the spinel oxide lattice with the addition of a small amount of Fe2+ located on octahedral sites. The Ni2+ orbital to spin moment ratio (μℓ/μs), derived from the application of XMCD sum rules, is enhanced for the substrates with a small lattice mismatch relative to NiFe2O4. The results suggest a path for increasing the orbital moment in NiFe2O4 by applying thin film growth techniques that can maintain a highly strained lattice for the NiFe2O4 film. 
    more » « less
  3. ; ; ; (, The Journal of Chemical Physics)
    MnO(001) thin films were grown on commercial MgO(001) substrates at 520 °C by reactive molecular beam epitaxy (MBE) using Mn vapor and O2-seeded supersonic molecular beams (SMBs) both with and without radio frequency (RF) plasma excitation. For comparison, MnO(001) films were grown by reactive MBE using O2 from a leak valve. X-ray photoelectron spectroscopy confirmed the Mn2+ oxidation state and 10%–15% excess oxygen near the growth surface. Reflection high-energy electron diffraction and x-ray diffraction evidenced that the films were rock salt cubic MnO with very strong (001) orientation. High-angle annular dark field scanning transmission electron microscopy with energy-dispersive x-ray spectroscopy demonstrated abrupt MnO/MgO interfaces and indicated [(001)MnO||(001)MgO] epitaxial growth. Ex situ atomic force microscopy of films deposited without RF excitation revealed smooth growth surfaces. An SMB-grown MnO(001) film was converted to Mn3O4 with strong (110) orientation by post-growth exposure to an RF-discharge (RFD) SMB source providing O atoms; the surface of the resultant film contained elongated pits aligned with the MgO110 directions. In contrast, using the RFD-SMB source for growth resulted in MnO(001) films with elongated growth pits and square pyramidal hillocks aligned along the MgO110 and 100 directions, respectively. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al (, Applied Physics Letters)
    The ability to accommodate multiple principal cations within a single crystallographic structure makes high entropy oxides (HEOs) ideal systems for exploring new composition–property relationships. In this work, the high-entropy design strategy is extended to strained single-crystal HEO-manganite (HEO-Mn) thin films. Phase-pure orthorhombic films of (Gd0.2La0.2Nd0.2Sm0.2Sr0.2)MnO3 were deposited on three different single-crystal substrates: SrTiO3 (STO) (100), NdGaO3 (110), and LaAlO3 (LAO) (100), each inducing different degrees of epitaxial strain. Fully coherent growth of the thin films is observed in all cases, despite the high degree of lattice mismatch between HEO-Mn and LAO. Magnetometry measurements reveal distinct differences in the magnetic properties between epitaxially strained HEO-Mn thin films and their bulk crystalline HEO counterparts. In particular, the bulk polycrystalline HEO-Mn shows two magnetic transitions as opposed to a single one observed in epitaxial thin films. Moreover, the HEO-Mn film deposited on LAO exhibits a significant reduction in the Curie temperature, which is attributed to the strong variation of the in-plane lattice parameter along the thickness of the film and the resulting changes in the Mn–O–Mn bond geometry. Thus, this preliminary study demonstrates the potential of combining high entropy design with strain engineering to tailor the structure and functionality of perovskite manganites. 
    more » « less
  5. ; ; ; ; ; ; ; ; (, Advanced Electronic Materials)
    Abstract Magnetic insulators, such as the rare‐earth iron garnets, are promising materials for energy‐efficient spintronic memory and logic devices, and their anisotropy, magnetization, and other properties can be tuned over a wide range through selection of the rare‐earth ion. Films are typically grown as epitaxial single crystals on garnet substrates, but integration of these materials with conventional electronic devices requires growth on Si. The growth, magnetic, and spin transport properties of polycrystalline films of dysprosium iron garnet (DyIG) with perpendicular magnetic anisotropy (PMA) on Si substrates and as single crystal films on garnet substrates are reported. PMA originates from magnetoelastic anisotropy and is obtained by controlling the strain state of the film through lattice mismatch or thermal expansion mismatch with the substrates. DyIG/Si exhibits large grain sizes and bulk‐like magnetization and compensation temperature. Polarized neutron reflectometry demonstrates a small interfacial nonmagnetic region near the substrate. Spin Hall magnetoresistance measurements conducted on a Pt/DyIG/Si heterostructure demonstrate a large interfacial spin mixing conductance between the Pt and DyIG comparable to other garnet/Pt heterostructures. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email