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2D Magnetic Systems
Published in Ram K. Gupta, Sanjay R. Mishra, Tuan Anh Nguyen, Fundamentals of Low Dimensional Magnets, 2023
Magnetic circular dichroism measures the difference in the absorption of right circularly and left circularly polarized light, due to the different contributions of magnetization to the real part of optical conductivity, σ of the sample. If the wavelength of polarized light lies in the X-ray range, it is called X-ray magnetic circular dichroism (XMCD). MOKE measures the changes in the polarization by measuring the angle of rotation of polarized light, while XMCD/MCD measure the changes in the ellipticity of the reflected polarized light. The ellipticity of polarized light depends on the real part of optical conductivity, which further depends on the sign of magnetization. The MCD measurement does not require any background subtraction in comparison to the MOKE signal. The extraction of optical conductivity values is difficult as there can be intermixing of real and imaginary parts in both MOKE and MCD signals, but these techniques are very sensitive in detecting even very small magnetic moments of any monolayer. The signal-to-noise ratio can be improved by using wavelengths that are resonant with the optical transitions of the magnetized samples. Both the MOKE and MCD techniques have been mainly used for Ising type and Heisenberg type 2D magnets because they can probe out-of-plane magnetization only. The comparison of MOKE and field-dependent MCD measurements on the CrI3 monolayer and bilayer is shown in Figure 5.2a–c. To probe the magnetism of XY 2D magnet and 2D magnetic semiconductor, inelastic light scattering–based measurements are used. Although the use of X-rays instead of the laser source in MCD can help to measure the in-plane magnetization along with a determination of elements by X-rays, giving the spin and orbital momentum of magnetic atoms in XMCD [27].
Inverse estimation of parameters for the magnetic domain via dynamics matching using visual-perceptive similarity
Published in Science and Technology of Advanced Materials: Methods, 2022
Ryo Murakami, Masaichiro Mizumaki, Ichiro Akai, Hayaru Shouno
Magnetic materials are used in industrial equipment such as sensors, indicators, and transformers, as well as in large equipment such as automobiles, trains, and aircraft. The performance of magnetic devices is governed by the magnetic domain parameters (e.g. magnetic anisotropy, exchange interaction, dipole interaction) of magnetic materials; however, it is difficult to observe the magnetic domain parameters directly. Therefore, the time evolution of magnetic domain patterns formed by magnetic spins was observed in the research and development of magnetic materials [1]. The magnetic domain is a region wherein almost all spins point in the same direction. Magnetic domain patterns (i.e. texture structure) are formed by exchange and dipole interactions between magnetic spins; various patterns appear depending on the magnetic domain parameters [2,3]. Advances in measurement technology have enabled us to measure magnetic domain patterns and obtain information on the magnetic domain parameters of materials from spin dynamics. Coherent X-ray diffraction imaging and scanning microscopy based on X-ray magnetic circular dichroism are powerful methods in terms of element selectivity and high spatial resolution [4,5].
Heusler alloys for spintronic devices: review on recent development and future perspectives
Published in Science and Technology of Advanced Materials, 2021
Kelvin Elphick, William Frost, Marjan Samiepour, Takahide Kubota, Koki Takanashi, Hiroaki Sukegawa, Seiji Mitani, Atsufumi Hirohata
As a direct method to estimate the element specific magnetic moments per atom, X-ray magnetic circular dichroism (XMCD) has been exploited. XMCD measurements are performed at the L2 and L3 absorption edges of the constituent elements of the Heusler alloys, which represent the X-ray-induced excitation from the 2p1/2 and 2p3/2 core levels into the valence d states, respectively [178]. A magnetic field is applied perpendicular to the sample films, realising the magnetisation of the samples to be aligned parallel (or antiparallel) to the incident circularly polarised X-rays. These two configurations provide the corresponding X-ray absorption spectra, both of which are measured by the total electron yield method, revealing the difference in the population between up and down spin electrons. The difference in absorption cross-sections represents the XMCD signals as a result. Since the orbital part of the atomic wavefunction interacts with the circularly polarised X-rays [179], which indirectly interact with the spins of the atoms through the spin–orbit interaction [180], non-zero XMCD signals can be observed in the vicinity of the L2 and L3 edges. By applying the sum rules [179–181] after relevant background subtraction, element specific spin magnetic moments per atom mspin are estimated as listed in Table 4.
Rare-earth-doped Bi2X3 (X = Se, Te) as candidates for magnetic topological insulators
Published in Philosophical Magazine, 2020
J.-S. Kang, Eunsook Lee, Seungho Seong, Min Young Yang, Jinsu Kim, Myung-Hwa Jung, Byeong-Gyu Park, Younghak Kim, Geunyong Kim, Jeehoon Kim
In this work, we have studied the electronic structures of R-doped (; ) single crystals as candidates for magnetic-TIs, employing soft X-ray absorption spectroscopy (XAS) [19], soft X-ray magnetic circular dichroism (XMCD) [20], angle-resolved photoemission spectroscopy (ARPES) [21], and circular dichroism (CD) ARPES [22,23]. XAS and XMCD provide direct information on the valence states and the element-specific magnetic moments of the constituent ions, respectively [19,20,24]. ARPES is a powerful experimental tool in determining electronic structures of TIs [6–8,25–27]. CD-ARPES allows one to observe a helical spin texture of the topological surface state (TSS) across the Dirac point (DP) directly [22,28,29].