Journal of Physics; Condensed Matter, 28(15), p.153002_1 - 153002_31, 2016/04
Chen, Y.-T.*; Takahashi, Saburo*; Nakayama, Hiroyasu*; Althammer, M.*; Goennenwein, S. T. B.*; Saito, Eiji; Bauer, G. E. W.*
Journal of Physics; Condensed Matter, 28(10), p.103004_1 - 103004_15, 2016/03
We review the so-called spin Hall magnetoresistance (SMR) in bilayers of a magnetic insulator and a metal, in which spin currents are generated in the normal metal by the spin Hall effect. The associated angular momentum transfer to the ferromagnetic layer and thereby the electrical resistance is modulated by the angle between the applied current and the magnetization direction. The SMR provides a convenient tool to non-invasively measure the magnetization direction and spin-transfer torque to an insulator. We introduce the minimal theoretical instruments to calculate the SMR, i.e. spin diffusion theory and quantum mechanical boundary conditions. This leads to a small set of parameters that can be fitted to experiments. We discuss the limitations of the theory as well as alternative mechanisms such as the ferromagnetic proximity effect and Rashba spin-orbit torques, and point out new developments.
Ikeuchi, Kazuhiko*; Kobayashi, Yoshiaki*; Suzukia, Kazunori*; Ito, Masayuki*; Kajimoto, Ryoichi; Bourges, P.*; Christianson, A. D.*; Nakamura, Hiroki; Machida, Masahiko; Sato, Masatoshi*
Journal of Physics; Condensed Matter, 27(46), p.465701_1 - 465701_7, 2015/11
We report the results of inelastic neutron scattering measurements on particular phonons of a superconducting (SC) CaPtAs(FePtAs) with the onset transition temperature K to investigate mainly what roles orbital fluctuation plays in Cooper pairing, where we observed a slight softening of the in-plane transverse acoustic mode corresponding to the elastic constant . This softening starts at temperature well above the SC , as decreases. An anomalously strong change of the scattering intensity of in-plane optical modes was observed at the M point of the pseudo tetragonal reciprocal space in the range of 35 40 meV with decreasing from far above . Because this region mainly corresponds to the motion of Fe and As atoms in the FeAs planes, the finding presents information on the coupling between the orbital fluctuation of Fe electrons and the lattice system, useful for studying the possible roles of orbital fluctuation in the pairing mechanism and/or the appearance of the so-called nematic phase.
Li, H.; Maekawa, Masaki; Kawasuso, Atsuo; Tanimura, Naoki*
Journal of Physics; Condensed Matter, 27(24), p.246001_1 - 246001_5, 2015/06
Uchida, Kenichi*; Ishida, Masahiko*; Kikkawa, Takashi*; Kirihara, Akihiro*; Murakami, Tomoo*; Saito, Eiji
Journal of Physics; Condensed Matter, 26(34), p.343202_1 - 343202_15, 2014/08
Mori, Michiyasu; Koshibae, Wataru*; Hikino, Shinichi*; Maekawa, Sadamichi
Journal of Physics; Condensed Matter, 26(25), p.255702_1 - 255702_5, 2014/06
Chudo, Hiroyuki; Koutroulakis, G.*; Yasuoka, Hiroshi; Bauer, E. D.*; Tobash, P. H.*; Mitchell, J. N.*; Thompson, J. D.*
Journal of Physics; Condensed Matter, 26(3), p.036001_1 - 036001_5, 2014/01
The results of In nuclear quadrupole resonance (NQR) measurements on PuIn are reported. Three of the four NQR lines of In expected for nuclear spin =9/2 are observed. The equal spacing of these lines at 20 K yields the NQR frequency of =10.45 MHz, and the asymmetry parameter of the electric field gradient, =0. The NQR line profile and the nuclear spin-lattice relaxation rate display an abrupt change at 14 K, which is associated with the onset of long-range antiferromagnetic order. The temperature dependences of the staggered magnetization , extracted from the NQR spectra, and below =14 K are well explained by the self-consistent renormalization (SCR) theory for spin fluctuations. In addition, scaling between and is also consistent with the predictions of SCR theory, providing further evidence that PuIn is a weak itinerant antiferromagnet in which spin fluctuations around the antiferromagnetic wave vector play a major role in the system's behavior at finite temperatures.
Mitsumoto, Keisuke*; Goto, Saori*; Nemoto, Yuichi*; Akatsu, Mitsuhiro*; Goto, Terutaka*; Dung, N. D.*; Matsuda, Tatsuma; Haga, Yoshinori; Takeuchi, Tetsuya*; Sugiyama, Kiyohiro*; et al.
Journal of Physics; Condensed Matter, 25(29), p.296002_1 - 296002_8, 2013/07
Ye, M.*; Kuroda, Kenta*; Takeda, Yukiharu; Saito, Yuji; Okamoto, Kazuaki*; Zhu, S.-Y.*; Shirai, Kaito*; Miyamoto, Koji*; Arita, Masashi*; Nakatake, Masashi*; et al.
Journal of Physics; Condensed Matter, 25(23), p.232201_1 - 232201_5, 2013/06
no abstracts in English
Tsuru, Tomohito; Udagawa, Yutaka; Yamaguchi, Masatake; Itakura, Mitsuhiro; Kaburaki, Hideo; Kaji, Yoshiyuki
Journal of Physics; Condensed Matter, 25(2), p.022202_1 - 022202_5, 2013/01
There is a pressing need to improve the ductility of magnesium alloy toward the advanced application for light-weight structural materials. In this letter we focused attention on the particular potential function for yttrium to activate the non-basal slip. The generalized stacking fault (GSF) energies of both basal and prismatic planes for pure magnesium are calculated by density functional theory (DFT) and EAM potential, and its effect on the dislocation core structures are examined by semidiscrete variation Peierls Nabarro (SVPN) model. Solution softening of added yttrium was similarly estimated by combination of DFT and SVPN model. Yttrium was found to have a particular influence on solution softening by the reduction of the gradient of the GSF energy.
Kobayashi, Hisao*; Ikeda, Shugo*; Sakaguchi, Yui*; Yoda, Yoshitaka*; Nakamura, Hiroki; Machida, Masahiko
Journal of Physics; Condensed Matter, 25(2), p.022201_1 - 022201_6, 2013/01
The electronic and vibrational properties of EuFeAs in the tetragonal phase between 0 and 5 GPa have been investigated using Fe Mssbauer spectroscopy and Fe nuclear resonance inelastic scattering, respectively. We find a discontinuous increase of the center shift around 2.3 GPa, reflecting a change of the electronic state of Fe, and above 2.5 GPa a softening of the optical phonon modes associated with an increase of the relative volume of the FeAs tetrahedron in the unit cell. Our findings reveal that an effective As-As hybridization along the c axis appears at approximately 2.3 GPa in the tetragonal phase of EuFeAs, along with a change in the electronic state of Fe, causing bulk superconductivity to appear at a low temperature. Consequently, the change in the electronic state of the Fe atom and the effective As-As hybridization play key roles in the pressure-induced superconductivity in the tetragonal phase of AFeAs.
Hashinokuchi, Michihiro*; Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Michio*
Journal of Physics; Condensed Matter, 24(39), p.395007_1 - 395007_8, 2012/10
Kishi, Hirofumi*; Padama, A. A. B.*; Arevalo, R. L.*; Moreno, J. L. V.*; Kasai, Hideaki*; Taniguchi, Masashi*; Uenishi, Mari*; Tanaka, Hirohisa*; Nishihata, Yasuo
Journal of Physics; Condensed Matter, 24(26), p.262001_1 - 262001_5, 2012/07
no abstracts in English
Padama, A. A. B.*; Kishi, Hirofumi*; Arevalo, R. L.*; Moreno, J. L. V.*; Kasai, Hideaki*; Taniguchi, Masashi*; Uenishi, Mari*; Tanaka, Hirohisa*; Nishihata, Yasuo
Journal of Physics; Condensed Matter, 24(17), p.175005_1 - 175005_6, 2012/05
no abstracts in English
Hayashi, Koichi*; Happo, Naohisa*; Hosokawa, Shinya*; Hu, W.; Matsushita, Tomohiro*
Journal of Physics; Condensed Matter, 24(9), p.093201_1 - 093201_15, 2012/03
Li, D. X.*; Kimura, Akihiro*; Haga, Yoshinori; Nimori, Shigeki*; Shikama, Tatsuo*
Journal of Physics; Condensed Matter, 23(7), p.076003_1 - 076003_7, 2011/02
Yoneda, Yasuhiro; Sakamoto, Wataru*
Journal of Physics; Condensed Matter, 23(1), p.015902_1 - 015902_5, 2011/01
The electric structure of BiFeO (BFO), BiFeO-PbTiO solid solution (BFO-PT), and Mn-doped BFO-PT (BFM-PT) films fabricated by chemical solution deposition were investigated by X-ray absorption fine structure (XAFS). The valence fluctuation of iron atoms was closely connected with the leakage current properties. The charge fluctuated BFO film showed leaky feature, and the charge ordered BFO-PT and BFM-PT films were improved leakage current property. The valence fluctuation of iron atoms can be controlled by Mn and Ti substitutions.
Takahashi, Masamitsu; Tamura, Kazuhisa; Mizuki, Junichiro; Kondo, Toshihiro*; Uosaki, Kohei*
Journal of Physics; Condensed Matter, 22(47), p.474002_1 - 474002_9, 2010/12
Journal of Physics; Condensed Matter, 22(47), p.474007_1 - 474007_7, 2010/12
A strontium or strontium oxide epitaxial layer was grown using a monoatomic buffer layer of hydrogen on silicon, in spite of a huge lattice mismatch. The onset of the initial growth stage of strontium crystals occur with only one atomic layer deposition. To investigate the growth mechanism in the highly mismatched system, combination analysis using neutron reflection, reflection high-energy electron diffraction, X-ray photoelectron spectra, and stress measurements is employed. The interface structure has opened up a new way to fabricate novel heterostructures, consisting of various kinds of one-, two- or three-dimensional materials for future silicon-based technology.
Sakai, Toru; Sato, Masahiro*; Okamoto, Kiyomi*; Okunishi, Koichi*; Itoi, Chigaku*
Journal of Physics; Condensed Matter, 22(40), p.403201_1 - 403201_13, 2010/10
Recent developments of theoretical studies on spin nanotubes are reviewed, especially focusing on the S=1/2 three-leg spin tube. In contrast to the three-leg spin ladder, the tube has a spin gap in case of the regular-triangle unit cell when the rung interaction is sufficiently large. The effective theory based on the Hubbard Hamiltonian indicates a quantum phase transition to the gapless spin liquid due to the lattice distortion to an isosceles triangle. This is also supported by the numerical diagonalization and the density matrix renormalization group analyses. Furthermore, combining analytical and numerical approaches, we reveal several novel magnetic-field-induced phenomena: Nel, dimer, chiral and/or inhomogeneous orders, new mechanism for the magnetization plateau formation, and others. The recently synthesized spin tube materials are also briefly introduced.