http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Spin-wave eigenmodes in single disk-shaped FeB nanomagnet
Cho, Jaehun,Miwa, Shinji,Yakushiji, Kay,Tamaru, Shingo,Kubota, Hitoshi,Fukushima, Akio,Fujimoto, Satoshi,Tamura, Eiiti,You, Chun-Yeol,Yuasa, Shinji,Suzuki, Yoshishige American Physical Society 2016 Physical Review B Vol.94 No.18
<P>Spin-wave eigenmodes in a disk-shaped FeB nanomagnet were investigated using magnetic tunnel junctions with a FeB magnetic layer and MgO barrier. Noise spectrum measurements for a perpendicularly magnetized junction of 120 nm in diameter showed thermal excitation of distinct spin-wave modes. The measured spectra were compared with analytical calculations and numerical simulations. As a result, the observed modes were classified as spin-wave eigenmodes with various nodal circles and nodal diameter modes by taking into account splitting between directional spin-wave modes originating from dynamic dipolar interaction instead of Dzyaloshinskii-Moriya interaction. These results provide a fundamental understanding of spin dynamics in nanosize spintronic devices.</P>
Cho, Jaehun,Kim, Nam-Hui,Kang, Seung Ku,Hwang, Hee-Kyeong,Jung, Jinyoung,Swagten, Henk J M,Kim, June-Seo,You, Chun-Yeol IOP 2017 Journal of Physics. D, Applied Physics Vol.50 No.42
<P>We investigate the sign of the interfacial Dzyaloshinskii–Moriya interaction (iDMI) energy density in system with inversion symmetry breaking for amorphous and polycrystalline ferromagnetic layers (CoFeB, Co) sandwiched by two different or the same heavy metals (Pt, Ta). By employing Brillouin light scattering, we observe non-reciprocal spin-wave dispersions which is a fingerprint of iDMI in SiO<SUB>2</SUB>/(Pt,Ta)/(CoFeB, Co)/(Pt,Ta) systems. We carefully confirm that the signs of DMI of structurally inverted systems are changed accordingly. Negative iDMI for SiO<SUB>2</SUB>/Pt/(CoFeB, Co)/Ta and positive iDMI for SiO<SUB>2</SUB>/Ta/(CoFeB, Co)/Pt are observed, and iDMI of the symmetric structures (Pt/CoFeB/Pt and Ta/CoFeB/Ta) are not measureable with our Brillouin light scattering setup due to a negligible iDMI. For amorphous CoFeB, the magnitudes of iDMI are the same within the experimental error regardless the stacking order. For the textured Co, however, the magnitude of iDMI for Pt/Co/Ta is about 30 % larger than Ta/Co/Pt structure.</P>
Introduction of Brillouin Light Scattering for Spintronics Research
Jaehun Cho,June-Seol Kim,Chun-Yeol You 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2
We will explain about Brillouin Light Scattering (BLS), which is an in-elastic light scattering with magnon of the magnetic samples. Magnon excitation frequency (or spin-wave (SW) resonance frequency) is determined by the dispersion relations of SW as a function of the basic magnetic properties of the samples, sample’s geometrical structure, SW wavevector, and external magnetic field. In BLS measurement, we varied the external magnetic field and obtained the basic magnetic properties of the sample by non-linear regression process, so that we can determine the saturation magnetization, anisotropy energy, exchange stiffness. In addition, we can also determine the interfacial Dzyaloshinskii-Moriya Interaction (iDMI) energy density by using non-reciprocal nature of the SW with non-zero iDMI. Since BLS is based on optical measurement, BLS has a lateral resolution of the laser beam spot size (~50 um), and BLS can measure the magnetic properties of the sub-nm ferromagnetic films. In this lecture, we will discuss about basic principles of BLS measurement and application of BLS for spintronics devices researches.
Cho, Jaehun,Kim, Nam-Hui,Jung, Jinyong,Han, Dong-Soo,Swagten, Henk J. M.,Kim, June-Seo,You, Chun-Yeol IEEE 2018 IEEE transactions on magnetics Vol.54 No.6
<P>We investigate the interfacial Dzyaloshinskii–Moriya interaction (iDMI) and the perpendicular magnetic anisotropy (PMA) in the annealed inversion symmetry breaking structures (Pt/Co (CoFeB)/AlO<SUB><I>x</I></SUB> and Ta/CoFeB/AlO<SUB><I>x</I></SUB>) by Brillouin light scattering. The iDMI energy density of Pt/Co and Pt/CoFeB samples decreases while increasing annealing temperature, but the iDMI energy density of Ta/CoFeB sample slightly increases by increasing annealing temperature. By applying the thermal annealing process, PMA energies slightly increase at the Pt/Co interface; however, Pt/CoFeB, (Ta/CoFeB) structures are dramatically decreased (increased) by the annealing process. The effects of the annealing show complicate variation for iDMI and PMA for each structure; however, we find overall weak correlations between iDMI and PMA despite different materials and annealing process.</P>