Kyushu University Academic Staff Educational and Research Activities Database
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NAKAGAWA Takeshi Last modified date:2019.06.28



Graduate School
Undergraduate School


Academic Degree
Doctor of Science
Country of degree conferring institution (Overseas)
No
Field of Specialization
Surface Science
Total Priod of education and research career in the foreign country
00years06months
Outline Activities
My research interest is structures and properties of surfaces and thin films. Most works are related to surface magnetic properties. I'm developing novel methods to measure surface magnetism in synchrotron facilities and to observe surface magnetic domain structures using lasers.
Research
Research Interests
  • Investigation of giant magnetic anisotropy and coercivity in nanostructure on transition metal surfaces
    keyword : anisotropy,coercivity,surface magnetism
    2013.04~2015.03.
  • Geometrical and electronic structure of two dimensional surface. Surface magnetism. Surface observation by photoemission electron microscope
    keyword : surface, magnetism, photoemission electron microscopy
    2012.11.
  • Geometrical and electronic structure of two dimensional surface. Surface magnetism. Surface observation by photoemission electron microscope
    keyword : surface, magnetism, photoemission electron microscopy
    2012.11.
Current and Past Project
  • Invesitgation of surface magnetism of Fe and Co on W surfaces has been done using spin polarized scanning tunneling microscope (in Germany) and magnetic circular dichroism measurement (in Japan)
  • The project reveal changes of magnetic domain structures using a newly developed magnetic circular dichorism photoemission electron microscope. The current work is on the magnetic domain structure changes of a Ni surface induced by hydrogen molecular adsorption.
  • The project reveal changes of magnetic domain structures using a newly developed magnetic circular dichorism photoemission electron microscope. The current work is on the magnetic domain structure changes of a Ni surface induced by hydrogen molecular adsorption.
Academic Activities
Papers
1. NAKAGAWA Takeshi, Oscillations of the Orbital Magnetic Moment due to d-Band Quantum Well States, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.113.067203, 113, 6, 2014.08.
2. T. Nakagawa, and T. Yokoyama, Laser induced threshold photoemission magnetic circular dichroism and its application to photoelectron microscope, Journal of Electron Spectroscopy and Related Phenomena, 186, 356, 2012.12, This work enlightens the threshold photoemission magnetic circular dichroism (MCD) and its adaption on photoemission electron microscopy (PEEM) using lasers. MCD is a simple and efficient way to investigate magnetic properties since it does not need any spin analyzers with low efficiency, and thus the MCD related techniques have developed to observe magnetic domains. Usually, MCD in a total yield measurement in the valence band with weak spin–orbit coupling (SOC) excited by low photon energy (hν≤ 6 eV) does not compete with the X-ray magnetic circular dichroism (XMCD) with strong SOC. XMCD PEEM observation of magnetic domains has been successfully established while MCD PEEM derived from valence bands has not been. However, using angle and energy resolved photoelectron, valence band MCD provides large asymmetry similar to that by XMCD. Threshold measurement of photoelectron in a total electron yield procedure can take advantage of the measurement of photoelectrons with a limited angle and energy mode. This restriction of the photoelectron makes the threshold MCD technique an efficient way to get magnetic information and gives more than 10% asymmetry for Ni/Cu(0 0 1), which is comparable to that obtained by angle resolved photoemission. Thus the threshold MCD technique is a suitable method to observe magnetic domains by PEEM. For threshold MCD, incident angle dependence and high sensitivity to out-of-plane magnetized films compared with in-plane ones are discussed. Ultrashort pulse lasers make it feasible to measure two photon photoemission MCD combined with PEEM, where resonant excitation has a possibility to enhance dichroic asymmetry. Recent results for valence band magnetic dichroism PEEM are presented..
3. T. Nakagawa, Y. Takagi, T. Yokoyama, T. Methfessel, S. Diehl, H.J. Elmers, Giant Magnetic Anisotropy Energy and Coercivity in Fe island and atomic wire on W(110), Phys. Rev. B, 86, 144418, 2012.11, We have directly investigated the giant magnetic anisotropy energy and coercivity of monolayer (ML) Fe islands and stripes on flat and stepped W(110) surfaces using x-ray magnetic circular dichroism. Both for islands and stripes, the magnetic anisotropy energy is ∼1.0 meV/atom, independent of the coverage below 0.5 ML. On the contrary, the coercive field of the islands rapidly drops from 4.3 T at 0.25 ML to 1.9 T at 0.50 ML, while that of the stripes moderately degrades from 3.5 T at 0.15 ML (∼3 atom rows) to 3.0 T at 0.50 ML. We explain the contrastive behavior for the islands and stripes by different nucleation and remagnetization processes. Considering the enhanced Fe moment, we find an unprecedented large value of the energy product BHmax=5 MJ/m3..
Presentations
1. M.T. Kibria, T. Nomitsu, T. Nakagawa and S. Mizuno, Investigation of Magnetic Dead Layer on Iron Silicide Surfaces, International Symposium on Surface Science(ISSS8), 2017.10, We report the magnetic dead layer at the interfaces between Fe and Si(111) surfaces. From the thickness dependent magnetization measurements, we decided the magnetic dead layer for Fe/c(8×4) silicide, Fe/p(2×2) silicide, and Fe/Si(111)-7×7 to be 3.0 ML, 5.0 ML, and 7.5 ML, respectively. Our results indicate that the c(8×4) iron silicide surface prevents further silicide formation more effectively than the
p(2×2) silicide and Si(111)-7×7 surface..
2. NAKAGAWA Takeshi, Imaging of ferromagnetic ultrathin films using threshold magnetic circular dichroism PEEM, PEEM Workshop6 , 2015.11.
3. NAKAGAWA Takeshi, Non-parallel alignment of Co spins on W(110), ICMFS2015, 2015.07.
Membership in Academic Society
  • Physical Society of Japan
  • The Surface Science Society of Japan
  • The Japanese Society for Synchrotron Radiation Research
Educational
Educational Activities
Undergraduate:
Department of Energy Science and Engineering
Graduate course:
Interdisciplinary Graduate School of Engineering Sciences
Other Educational Activities
  • 2015.03.