Magnetic Anisotropy Characterization with Structural Transitions in Fe/Co Bilayers by PEEM
ORAL
Abstract
Magnetic anisotropy, a crucial factor that represents the energy associated with magnetization rotation away from the easy axis, reflects the intrinsic properties of magnetic systems [1]. The investigation of magnetic anisotropy provides a deeper understanding of the responses to external magnetic fields and enables the prediction of their potential evolutions. However, magnetic anisotropy becomes complex due to interlayer coupling [2-4] and crystal structure [2,5] in multilayer systems, which are widely explored for advanced spintronic applications. To address this challenge, we fabricated a Fe/Co double wedge system and utilized the photoelectron emission microscope equipped with X-ray magnetic circular dichroism (XMCD-PEEM) to resolve the evolution of the magnetic domain as a function of thickness.
This study was conducted in situ under UHV conditions at the TLS-05B2 endstation of the National Synchrotron Radiation Research Center (NSRRC), Taiwan. The Fe/Co double wedge was deposited on Au(111) by EFM3 evaporators to precisely control the slope gradient at 1.00 ML per 30 μm. The correlated out-of-plane and in-plane magnetization components were verified through our domain contrast analysis method, which is based on the projection of photon helicity onto the normalized magnetization (σ · M), without the need of sample rotation. Two spin reorientation transition (SRT) regimes exhibit clear linear behavior with thickness, which is well described by our phenomenological model. The model reveals the corresponding magnetic anisotropy constants of −573 kJ/m³ for fcc-Co and −1199 kJ/m³ for fcc-Fe, confirming a structural evolution from an fcc-Fe/hcp-Co to a bcc-Fe/fcc-Co configuration. Furthermore, the coincidence of magnetic domain configurations between Fe and Co demonstrates the presence of ferromagnetic interlayer coupling. Therefore, these results prove the feasibility of detailed magnetic anisotropy investigation with ferromagnetic coupling and additional structural transition.
[1] A. Hirohata, et al., IEEE Trans. Magn. 51, 1–11 (2015).
[2] M. T. Johnsondag, et al., Rep. Prog. Phys. 59, 1409 (1996).
[3] T. Kasuya, Prog. Theor. Phys. 16, 45–57 (1956).
[4] J. Schöpf, et al., Phys. Rev. Mater. 8, 094410 (2024).
[5] G. H. O. Daalderop, et al., Phys. Rev. B 41, 11919–11937 (1990).
This study was conducted in situ under UHV conditions at the TLS-05B2 endstation of the National Synchrotron Radiation Research Center (NSRRC), Taiwan. The Fe/Co double wedge was deposited on Au(111) by EFM3 evaporators to precisely control the slope gradient at 1.00 ML per 30 μm. The correlated out-of-plane and in-plane magnetization components were verified through our domain contrast analysis method, which is based on the projection of photon helicity onto the normalized magnetization (σ · M), without the need of sample rotation. Two spin reorientation transition (SRT) regimes exhibit clear linear behavior with thickness, which is well described by our phenomenological model. The model reveals the corresponding magnetic anisotropy constants of −573 kJ/m³ for fcc-Co and −1199 kJ/m³ for fcc-Fe, confirming a structural evolution from an fcc-Fe/hcp-Co to a bcc-Fe/fcc-Co configuration. Furthermore, the coincidence of magnetic domain configurations between Fe and Co demonstrates the presence of ferromagnetic interlayer coupling. Therefore, these results prove the feasibility of detailed magnetic anisotropy investigation with ferromagnetic coupling and additional structural transition.
[1] A. Hirohata, et al., IEEE Trans. Magn. 51, 1–11 (2015).
[2] M. T. Johnsondag, et al., Rep. Prog. Phys. 59, 1409 (1996).
[3] T. Kasuya, Prog. Theor. Phys. 16, 45–57 (1956).
[4] J. Schöpf, et al., Phys. Rev. Mater. 8, 094410 (2024).
[5] G. H. O. Daalderop, et al., Phys. Rev. B 41, 11919–11937 (1990).
*The authors thank the National Science and Technology Council of Taiwan for financial support under Grant Nos. MOST 110-2112-M-110-016, MOST 111-2112-M-110-016, NSTC 112-2112-M-110-011, and NSTC 113-2112-M-110-004 for this project.
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Publication: Element-Resolved Magnetic Anisotropy and Structural Transitions in Fe/Co Bilayers
Presenters
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Liang-Wei Lan
- National Sun Yat-sen University