MaHoJeRo-Symposium September 8, 2017

Titles and Abstracts

At September 8, 2017 the MAINZ exchange program MaHoJeRo hosts renowned guests from Japan who will introduce their current research to us in a Symposium.

When: 09:00 - 12:00 am
Where: Lorentz-Raum, Staudingerweg 7, Room 05-127

Find below title and abstract of the speakers.

There will be free breakfast!




New layered structure of TM-Ga (TM = Mn and Co) alloys for advanced spintronic devices

Shigemi Mizukami, WPI Advanced Institute for Materials Research, Tohoku University, Japan

Ferrimagnetic L10 ordered MnGa alloy films exhibit a high perpendicular magnetic anisotropy and small Gilbert damping constant, which will be a promising material for advanced spintronic memory and/or ultrahigh frequency applications [1]. Recently we succeeded the growth of nano-layer of MnGa on the paramagnetic CoGa B2 ordered alloys [2]. By using this growth technique, we found the current-induced spin-orbit torque switching in the CoGa/MnGa/MgO layered structure. This switching may be caused by the spin-Hall effect in the paramagnetic CoGa alloys buffer even without heavy elements [3]. I will discuss these recent results in my talk. This study was partially supported by the KAKENHI and the ImPACT program.

[1] S. Mizukami, F. Wu, A. Sakuma, J. Walowski, D. Watanabe, T. Kubota, X. Zhang, H. Naganuma, M. Oogane, Y. Ando, and T. Miyazaki, Phys. Rev. Lett., 106, 17201 (2011).
[2] K. Z. Suzuki, R. Ranjbar, J. Okabayashi, Y. Miura, A. Sugihara, H. Tsuchiura, and S. Mizukami, Sci. Rep., 6, 30249 (2016).
[3] M. Takikawa, K. Z. Suzuki, R. Ranjbar, and S. Mizukami, Appl. Phys. Express, 10, 073004 (2017).


Laser-induced coherent terahertz-wave emission in the Ta/CoFeB/MgO hetero structurefilms

 Y. Sasaki, K.Z. Suzuki, A. Kamimaki and S. Mizukami; WPI Advanced Institute for Materials Research, Tohoku University, Japan 

Pulse laser-induced coherent terahertz-wave emission from The cemission ferromagnetic metal (FM) s/heavy metal (HM) layers due to inverse-spin Hall effect is one of the hot topics because the THz wave intensity and bandwidth are higher than that emitted from the conventional semiconductor crystal, such as ZnTe. However, there are many issues to be clarified; e.g., the dependence of THz wave emission intensity on magnetic material and spin polarization. In this study, we investigated thickness and annealing temperature dependence of laser-induced THz wave emission in Ta/CoFeB/MgO films to gain the insight into the relationship among magnetization, crystal structure and THz wave emission intensity.

[1] T. Kampfrath, et al., Nat. Nanotech. 8, 256-260 (2013)
[2] T. Seifert, et al., Nat. Photon. 10, 483-488 (2016)


Observation of nonequivalent Fermi-arc states of opposite surfaces in noncentrosymmetric Weyl semimetal NbP

Seigo Souma, Center for Spintronics Research Network & WPI Advanced Institute for Materials Research, Tohoku University, Japan

We have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) on noncentrosymmetric Weyl semimetal candidate NbP, and determined the electronic states of both Nb- and P-terminated surfaces corresponding to the “opposite” surfaces of a polar crystal [1]. We revealed a drastic difference in the Fermi-surface topology between the opposite surfaces, whereas the Fermi arcs on both surfaces are likely terminated at the surface projection of the same bulk Weyl nodes. Comparison of the ARPES data with our first-principles band calculations suggests notable difference in electronic structure at the Nb-terminated surface between theory and experiment. The present result opens a platform for realizing exotic quantum phenomena arising from unusual surface properties of Weyl semimetals.

[1] S. Souma, Z. Wang, H. Kotaka, T. Sato, K. Nakayama, Y. Tanaka, H. Kimizuka, T. Takahashi, K. Yamauchi, T. Oguchi, Kouji Segawa, and Yoichi Ando, Phys. Rev. B 93, 161112(R) (2016).