High-temperature Magnetodielectric $\mathrm{Bi}({\mathrm{Fe}}_{0.5}{\mathrm{Mn}}_{0.5}){\mathrm{O}}_{3}$ Thin Films with Checkerboard-Ordered Oxygen Vacancies and Low Magnetic Damping

High-temperature Magnetodielectric $Bi ({Fe}_{0.5} {Mn}_{0.5}) O_{3}$ Thin Films with Checkerboard-Ordered Oxygen Vacancies and Low Magnetic Damping

E. Coy, I. Fina, K. Załęski, A. Krysztofik, L. Yate, L. Rodriguez, P. Graczyk, H. Głowiński, C. Ferrater, J. Dubowik, and M. Varela

Phys. Rev. Applied 10, 054072 – Published 30 November 2018

Abstract

The possibility of affecting the magnetic properties of a material by dielectric means, and vice versa, remains an attractive perspective for modern electronics and spintronics. Here, we report on epitaxial $Bi ({Fe}_{0.5} {Mn}_{0.5}) O_{3}$ thin films with exceptionally low Gilbert damping and magnetoelectric coupling above room temperature ( $< 400$ K). The ferromagnetic order, not observed in bulk, has been detected with a total magnetization of 0.44 $μ_{B} /$ formula units with low Gilbert damping parameter (0.0034), both at room temperature. Additionally, a previously overlooked check-board ordering of oxygen vacancies is observed, providing insights on the magnetic and dielectric origin of the multifunctional properties of the films. Finally, intrinsic magnetodielectric behavior is observed as revealed by the variation of dielectric permittivity well above room temperature. These findings show the possibility of electric-field-controlled magnetic properties, in low Gilbert-damping-based spintronic devices, using single-phase multiferroic materials.

Received 6 April 2018
Revised 17 October 2018

DOI:https://doi.org/10.1103/PhysRevApplied.10.054072

Physics Subject Headings (PhySH)

Magneto-dielectric effect Spin waves Spintronics Vacancies

Multiferroics Perovskites Thin films Transition metal oxides

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

E. Coy^1,*, I. Fina^2,3, K. Załęski¹, A. Krysztofik⁴, L. Yate⁵, L. Rodriguez³, P. Graczyk⁴, H. Głowiński⁴, C. Ferrater³, J. Dubowik⁴, and M. Varela³

¹NanoBioMedical Centre, Adam Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland
²Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, 08193 Barcelona, Spain
³Departament de Física Aplicada, Universitat de Barcelona, Carrer de Martí i Franquès, 1, 08028 Barcelona, Spain
⁴Institute of Molecular Physics, Polish Academy of Sciences, ul. Smoluchowskiego 17, 60-179 Poznań, Poland
⁵CIC biomaGUNE, Paseo Miramón 182, 20014 Donostia-San Sebastian, Spain

^*coyeme@amu.edu.pl

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Vol. 10, Iss. 5 — November 2018

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Figure 1
Structural data of 40 nm $BFMO / STO (001)$ film. (a) The $2 Θ$ - $ω$ scan shows the $(001)$ texture of the film. Insets show a standard STO unit cell and the bulk ${Bi}_{2} Fe Mn O 6$ cells (see Table 1). (b) X-ray reflectometry experiments with an extracted thickness of approximately 43.5 nm and $R q \approx 1.2$ nm (fitting has been shifted down for clarity). (c) $ϕ$ scans performed around the STO(110) and BFMO(110) peak position showing cube-on-cube growth as sketched. (d) Reciprocal space map around the substrate $(103)$ reflection. The black line serves as a guide for the eye showing coincidence of BFMO and STO in-plane peak position.
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Figure 2
Transmission electron micrographs. (a) Low-magnification image of the films, showing the total thickness. Inset shows the interface congruence based in IFFT images. (b) SAED image collected from the film and substrate area. Bottom red arrows show the growth direction. Large dashed squares (red) represent the $STO$ diffraction peaks. The slightly reduced dashed square (blue) represents the BFMO lattice constants. The small dashed square (yellow) shows the alignment of the supercell peaks with the BFMO peaks. Small dots in the center of the image (yellow) show the position of the larger order peaks. (c) High-resolution image showing the origin of the small ordering observed in the SAED pattern and the corresponding organization in the BFMO lattice (left) and filtered image taking the high-order peaks with an inset of the crystal correspondence. (d) Atomic configuration of the ordered oxygen vacancies are shown in blue.
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Figure 3
Magnetic studies (a) SQUID magnetometry measurements $M (H)$ at 300 K. The inset shows the enlarged part of the hysteresis loop at low magnetic fields. (b) The FMR linewidth as a function of frequency. The shaded section marks the increase in FMR linewidth as a result of decreasing magnetization of the sample at corresponding fields. The inset shows the results of $f (H_{r})$ dependence. Dielectric response of the BFMO thin films (c) overlapped dielectric spectra for $ε^{'}$ and $ε^{″}$ for all the temperatures measured, the $T$ arrow shows the trend as temperature increases. Inset shows a schematic of the measurement configuration. (d) Nyquist plots for selected spectra, showing the high- and low-frequency contributions. $ν$ shows the frequency increment. Insets show the high-frequency regime and the associated circuit for each contribution. (e) Extracted values for the intrinsic dielectric permittivity (top) and resistivity (bottom) in the whole range of temperatures, for both magnetic and nonmagnetic measurements. (f) Dielectric permittivity (relative) changes as a function of temperature. Inset shows the values of the constant phase element (CPE) exponent( $α^{'}$ ) as a function of temperature with and without applied magnetic field.
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Physical Review Applied

High-temperature Magnetodielectric Bi(Fe0.5Mn0.5)O3 Thin Films with Checkerboard-Ordered Oxygen Vacancies and Low Magnetic Damping

E. Coy, I. Fina, K. Załęski, A. Krysztofik, L. Yate, L. Rodriguez, P. Graczyk, H. Głowiński, C. Ferrater, J. Dubowik, and M. Varela

Phys. Rev. Applied 10, 054072 – Published 30 November 2018

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High-temperature Magnetodielectric $Bi ({Fe}_{0.5} {Mn}_{0.5}) O_{3}$ Thin Films with Checkerboard-Ordered Oxygen Vacancies and Low Magnetic Damping