Antiferromagnetic domain switching modulated by an ultrathin Co interlayer in the Fe/Co/CoO/MgO(001) system

Yu Yang, Jianhui Liang, Qian Li, Gong Chen, Chao Zhou, Jia Xu, Lu Sun, Mengmeng Yang, Alpha T. N’Diaye, Zi Qiang Qiu, and Yizheng Wu

Phys. Rev. B 102, 024434 – Published 21 July 2020

Abstract

Using a combination of hysteresis loop, Kerr microscope, and x-ray magnetic circular dichroism measurements, we investigated the antiferromagnetic (AFM) domain switching process modulated by the sub-nm thick Co inserting layer in a single crystalline Fe/Co/CoO/MgO(001). The CoO AFM domain switching occurs at lower temperature for the thicker Co interlayer, and the activation energy barrier of CoO AFM domain switching decreases as the Co interlayer thickness increases. The exchange coupling strength between the AFM spins in CoO layer and the ferromagnetic spins in the Fe/Co bilayer is found to be independent of the Co layer thickness. Our results suggest an approach to modulate the dynamic properties of AFM domains with an interfacial modification.

Received 4 March 2020
Revised 17 June 2020
Accepted 23 June 2020

DOI:https://doi.org/10.1103/PhysRevB.102.024434

Physics Subject Headings (PhySH)

Antiferromagnetism Magnetization switching

Antiferromagnets Magnetic multilayers

Surface magneto-optical Kerr effect

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Yu Yang¹, Jianhui Liang ^1,*, Qian Li², Gong Chen³, Chao Zhou ¹, Jia Xu¹, Lu Sun¹, Mengmeng Yang², Alpha T. N’Diaye⁴, Zi Qiang Qiu ², and Yizheng Wu ^1,5,*

¹Department of Physics, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, People's Republic of China
²Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA
³NCEM, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
⁴Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
⁵Shanghai Research Center for Quantum Sciences, Shanghai, 201315, China

^*Corresponding authors: jianhuiliang13@fudan.edu.cn; wuyizheng@fudan.edu.cn

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Vol. 102, Iss. 2 — 1 July 2020

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Images

Figure 1
Typical RHEED patterns of (a) MgO(001), (b) CoO (4.5 nm)/MgO(001), (c) Co(0.7 nm)/CoO(4.5 nm)/MgO(001), and (d) Fe(34 nm)/Co(0.7 nm)/CoO(4.5 nm)/MgO(001) with the electron incident direction along MgO⟨110⟩.
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Figure 2
(a) Schematics of spin configurations in the Fe/CoO bilayer after field cooling. (b) Schematics of CoO AFM domain switching after the field sweeping cycles with the applied field perpendicular to the field cooling direction. (c) Hysteresis loops from Fe (34 nm)/CoO (4.5 nm)/MgO(001) at 107 K for $H ∥ H_{FC}$ and $H ⊥ H_{FC}$ during the magnetic field cycling. N denotes the cycling number.
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Figure 3
Representative hysteresis loops of (a) Fe(34 nm)/CoO(4.5 nm), (b) Fe(34 nm)/Co(0.5 nm)/CoO(4.5 nm), and (c) Fe(34 nm)/Co(1 nm)/CoO(4.5 nm) for $H ⊥ H_{FC}$ at 80 K during magnetic field cycling (N denotes the cycling number). The loop with $N = 1$ in (c) starts from the initial state right after field cooling process. (d) Co thickness dependence of splitting field $H_{S}$ in the Fe/Co/CoO system. The inset indicates the identical hysteresis loops with different Co interlayer thickness.
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Figure 4
(a) Remanent Kerr signal versus field cycling number N at different temperatures from the sample of Fe (34 nm)/Co(0.2 nm)/CoO (4.5 nm)/MgO(001). The red lines are the fitted results using Eq. (1). (b) and (c) Temperature dependence of the fitted $τ_{D}$ and σ, respectively. The red line in (b) is the fitting curve with Eq. (2). (d) Temperature-dependent relaxation time constant $τ_{D}$ for Fe/Co/CoO/MgO(001) with various Co thicknesses. The solid lines are fitted results with Eq. (2). (e) The energy barrier from the fitting as a function of the Co thickness. The dashed line is the linear fitting.
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Figure 5
(a) Schematic drawing of sample structure of Fe (34 nm)/CoO (4.5 nm). (b)–(f) Time-dependent domain evolution of Fe/CoO at remanent state after different numbers of field cyclings at 102 K with H decreased from a positive field (+800 Oe). The field cycling number N during the Kerr domain imaging is listed in each frame. (g) Schematic drawing of sample structure of Fe (34 nm)/Co(0.7nm)/CoO (4.5 nm). (h)–(l) Time-dependent remanent domain evolution of Fe/Co/CoO at 80 K.
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Figure 6
(a) Schematic drawing of sample structure. (b) Co $L_{2, 3}$ x-ray adsorption spectra and (c) XMCD spectra of Fe (2 nm)/CoO (4.5 nm) and Fe (2 nm)/Co(0.6 nm)/CoO (4.5 nm). (d) Co thickness dependent XMCD measured on the Fe(2 nm)/Co (wedge)/CoO (4.5 nm) sample. The solid line is the fitting curve.
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