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Lee, O.*; Yamamoto, Kei; Umeda, Maki; Zollitsch, C. W.*; Elyasi, M.*; Kikkawa, Takashi*; Saito, Eiji; Bauer, G. E. W.*; Kurebayashi, Hidekazu*
Physical Review Letters, 130(4), p.046703_1 - 046703_6, 2023/01
Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)Yamamoto, Kei; Yu, W.*; Yu, T.*; Puebla, J.*; Xu, M.*; Maekawa, Sadamichi*; Bauer, G.*
Journal of the Physical Society of Japan, 89(11), p.113702_1 - 113702_5, 2020/11
Times Cited Count:7 Percentile:63.86(Physics, Multidisciplinary)Nambu, Yusuke*; Barker, J.*; Okino, Yuki*; Kikkawa, Takashi*; Shiomi, Yuki*; Enderle, M.*; Weber, T.*; Winn, B.*; Graves-Brook, M.*; Tranquada, J. M.*; et al.
Physical Review Letters, 125(2), p.027201_1 - 027201_6, 2020/07
Times Cited Count:31 Percentile:92.29(Physics, Multidisciplinary)Oyanagi, Koichi*; Takahashi, Saburo*; Cornelissen, L. J.*; Shan, J.*; Daimon, Shunsuke*; Kikkawa, Takashi*; Bauer, G. E. W.*; Van Wees, B. J.*; Saito, Eiji
Nature Communications (Internet), 10, p.4740_1 - 4740_6, 2019/10
Times Cited Count:29 Percentile:89.38(Multidisciplinary Sciences)Kikkawa, Takashi*; Shen, K.*; Flebus, B.*; Duine, R. A.*; Uchida, Kenichi*; Qiu, Z.*; Bauer, G. E. W.*; Saito, Eiji
Physical Review Letters, 117(20), p.207203_1 - 207203_6, 2016/11
Times Cited Count:126 Percentile:97.63(Physics, Multidisciplinary)Hou, D.*; Qiu, Z.*; Iguchi, Ryo*; Sato, Koji*; Vehstedt, E. K.*; Uchida, Kenichi*; Bauer, G. E. W.*; Saito, Eiji
Nature Communications (Internet), 7, p.12265_1 - 12265_6, 2016/07
Times Cited Count:12 Percentile:65.16(Multidisciplinary Sciences)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
Times Cited Count:71 Percentile:61.66(Physics, Condensed Matter)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.
Geprgs, S.*; Kehlberger, A.*; Coletta, F.*; Qiu, Z.*; Guo, E.-J.*; Schulz, T.*; Mix, C.*; Meyer, S.*; Kamra, A.*; Althammer, M.*; et al.
Nature Communications (Internet), 7, p.10452_1 - 10452_6, 2016/02
Times Cited Count:131 Percentile:97.31(Multidisciplinary Sciences)Bottoni, S.*; Leoni, S.*; Fornal, B.*; Raabe, R.*; Rusek, K.*; Benzoni, G.*; Bracco, A.*; Crespi, F. C. L.*; Morales, A. I.*; Bednarczyk, P.*; et al.
Physical Review C, 92(2), p.024322_1 - 024322_8, 2015/08
Times Cited Count:19 Percentile:78.89(Physics, Nuclear)Schreier, M.*; Bauer, G. E. W.*; Vasyuchka, V.*; Flipse, J.*; Uchida, Kenichi*; Lotze, J.*; Lauer, V.*; Chumak, A.*; Serga, A.*; Daimon, Shunsuke*; et al.
Journal of Physics D; Applied Physics, 48(2), p.025001_1 - 025001_5, 2015/01
Times Cited Count:52 Percentile:88.45(Physics, Applied)Koutroulakis, G.*; Yasuoka, Hiroshi; Chudo, Hiroyuki; Tobash, P. H.*; Mitchell, J. N.*; Bauer, E. D.*; Thompson, J. D.*
New Journal of Physics (Internet), 16, p.053019_1 - 053019_12, 2014/05
Times Cited Count:6 Percentile:46.51(Physics, Multidisciplinary)We report In nuclear quadrupolar resonance (NQR) measurements on the heavy-fermion superconductor PuCoIn
, in the temperature range 0.29 K
75 K. The NQR parameters for the two crystallographically inequivalent In sites are determined, and their temperature dependence is investigated. A linear shift of the quadrupolar frequency with lowering temperature below the critical value
is revealed, in agreement with the prediction for composite pairing. The nuclear spin-lattice relaxation rate
clearly signals a superconducting (SC) phase transition at
2.3 K, with strong spin fluctuations, mostly in-plane, dominating the relaxation process in the normal state near to
. Analysis of the
data in the SC state suggests that PuCoIn
is a strong-coupling
-wave superconductor.
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
Times Cited Count:5 Percentile:25.24(Physics, Condensed Matter)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.
Althammer, M.*; Meyer, S.*; Nakayama, Hiroyasu*; Schreier, M.*; Altmannshofer, S.*; Weiler, M.*; Huebl, H.*; Geprgs, S.*; Opel, M.*; Gross, R.*; et al.
Physical Review B, 87(22), p.224401_1 - 224401_15, 2013/06
Times Cited Count:381 Percentile:99.39(Materials Science, Multidisciplinary)We experimentally investigate and quantitatively analyze the spin Hall magnetoresistance (SMR) effect in ferromagnetic insulator (FI)/Pt and FI/nonmagnetic metal/Pt hybrid structures. For the FI, we use either YIG, nickel ferrite, or magnetite and for the nonmagnet, Cu or Au. The SMR is theoretically ascribed to the combined action of spin Hall and inverse spin Hall effect in the Pt top layer. It therefore should characteristically depend upon the orientation of the magnetization in the adjacent ferromagnet and prevail even if an additional, nonmagnetic metal layer is inserted between Pt and the ferromagnet. Our experimental data corroborate these theoretical conjectures. Using the SMR theory to analyze our data, we extract the spin Hall angle and the spin diffusion length in Pt. For a spin-mixing conductance of m
, we obtain a spin Hall angle of 0.11
0.08 and a spin diffusion length of (1.5
0.5) nm for Pt in our samples.
Chen, Y.-T.*; Takahashi, Saburo*; Nakayama, Hiroyasu*; Althammer, M.*; Goennenwein, S. T. B.*; Saito, Eiji; Bauer, G. E. W.*
Physical Review B, 87(14), p.144411_1 - 144411_9, 2013/04
Times Cited Count:558 Percentile:99.68(Materials Science, Multidisciplinary)We present a theory of the spin Hall magnetoresistance (SMR) in multilayers made from an insulating ferromagnet F, such as yttrium iron garnet (YIG), and a normal metal N with spin-orbit interactions, such as platinum (Pt). The SMR is induced by the simultaneous action of spin Hall and inverse spin Hall effects and therefore a nonequilibrium proximity phenomenon. We compute the SMR in F|N and F|N|F layered systems, treating N by spin-diffusion theory with quantum mechanical boundary conditions at the interfaces in terms of the spin-mixing conductance. Our results explain the experimentally observed spin Hall magnetoresistance in N|F bilayers. For F|N|F spin valves we predict an enhanced SMR amplitude when magnetizations are collinear. The SMR and the spin-transfer torques in these trilayers can be controlled by the magnetic configuration.
Uchida, Kenichi*; Ota, Takeru*; Adachi, Hiroto; Xiao, J.*; Nonaka, Tatsumi*; Kajiwara, Yosuke*; Bauer, G. E. W.*; Maekawa, Sadamichi; Saito, Eiji
Journal of Applied Physics, 111(10), p.103903_1 - 103903_11, 2012/05
Times Cited Count:118 Percentile:96.24(Physics, Applied)Bauer, G. E. W.*; Saito, Eiji; Van Wees, B. J.*
Nature Materials, 11(5), p.391 - 399, 2012/05
Times Cited Count:1331 Percentile:98.31(Chemistry, Physical)Spintronics is about the coupled electron spin and charge transport in condensed-matter structures and devices. The recently invigorated field of spin caloritronics focuses on the interaction of spins with heat currents, motivated by newly discovered physical effects and strategies to improve existing thermoelectric devices. Here we give an overview of our understanding and the experimental state-of-the-art concerning the coupling of spin, charge and heat currents in magnetic thin films and nanostructures. Known phenomena are classified either as independent electron (such as spin-dependent Seebeck) effects in metals that can be understood by a model of two parallel spin-transport channels with different thermoelectric properties, or as collective (such as spin Seebeck) effects, caused by spin waves, that also exist in insulating ferromagnets. The search to find applications - for example heat sensors and waste heat recyclers - is on.
Yasuoka, Hiroshi; Koutroulakis, G.*; Chudo, Hiroyuki; Richmond, S.*; Veirs, D. K.*; Smith, A. I.*; Bauer, E. D.*; Thompson, J. D.*; Jarvinen, G. D.*; Clark, D. L.*
Science, 336(6083), p.901 - 904, 2012/05
Times Cited Count:46 Percentile:86(Multidisciplinary Sciences)Uchida, Kenichi*; Xiao, J.*; Adachi, Hiroto; Oe, Junichiro; Takahashi, Saburo; Ieda, Junichi; Ota, Takeru*; Kajiwara, Yosuke*; Umezawa, Hiromitsu*; Kawai, Hirotaka*; et al.
Nature Materials, 9(11), p.894 - 897, 2010/11
Times Cited Count:990 Percentile:99.87(Chemistry, Physical)Thermoelectric generation is an essential function in future energy-saving technologies. However, it has so far been an exclusive feature of electric conductors, a situation which limits its application; conduction electrons are often problematic in the thermal design of devices. Here we report electric voltage generation from heat flowing in an insulator. We reveal that, despite the absence of conduction electrons, the magnetic insulator LaYFe
O
can convert a heat flow into a spin voltage. Attached Pt films can then transform this spin voltage into an electric voltage as a result of the inverse spin Hall effect. The experimental result require us to introduce a thermally activated interface spin exchange between LaY
Fe
O
and Pt. Our findings extend the range of potential materials for thermoelectric applications and provide a crucial piece of information for understanding the physics of the spin Seebeck effect.
Futakawa, Masatoshi; Kogawa, Hiroyuki; Hasegawa, Shoichi; Ikeda, Yujiro; Riemer, B.*; Wendel, M.*; Haines, J.*; Bauer, G.*; Naoe, Takashi; Okita, Kohei*; et al.
Journal of Nuclear Materials, 377(1), p.182 - 188, 2008/06
Times Cited Count:28 Percentile:85.9(Materials Science, Multidisciplinary)no abstracts in English
Oishi, Kazuki; Heffner, R. H.; Ito, Takashi; Higemoto, Wataru; Morris, G. D.*; Bauer, E. D.*; Graf, M. J.*; Zhu, J.-X.*; Morales, L. A.*; Sarrao, J. L.*; et al.
Physica B; Condensed Matter, 403(5-9), p.1013 - 1014, 2008/04
Times Cited Count:0 Percentile:0(Physics, Condensed Matter)PuCoGa has attracted much interest because it is the first Pu-based superconductor, having an order of magnitude higher transition temperature
K than the isostructural heavy fermion superconductor CeCoIn
(
K). The mechanism of the superconductivity in PuCoGa
is still under investigation, though recent experiments and theory suggest a magnetic origin. A unique aspect of this compound is the self-irradiation damage because Pu (
Pu,
= 24,000 years) creates lattice defects which scatter electrons and, hence, break superconducting pairs. In order to elucidate the magnitude and temperature dependence of the magnetic penetration depth
, we have performed
SR measurements in the same PuCoGa
single crystals after 25 and 400 days of aging. We found that
decreased from 18.5K to 15K for the aged sample, yet a quasi-linear temperature dependence was found for the low-temperature
in both the fresh and aged sample, consistent with
-wave pairing symmetry. The magnitude of the muon spin relaxation rate
in the aged sample,
, where
and
are the superfluid density and the effective mass, respectively, is reduced by about 70% compared to fresh sample. This indicates that the scattering from self-irradiation induced defects is not in the limit of the conventional Abrikosov-Gor'kov pair-breaking theory, but rather in the limit of short coherence length (about 2nm in PuCoGa
) superconductivity.