Nonlinear magnon polaritons

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

https://doi.org/10.1103/PhysRevLett.130.046703

Non-reciprocal pumping of surface acoustic waves by spin wave resonance

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

https://doi.org/10.7566/JPSJ.89.113702

Spin transport in insulators without exchange stiffness

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

https://doi.org/10.1038/s41467-019-12749-7

Observation of temperature-gradient-induced magnetization

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

https://doi.org/10.1038/ncomms12265

Origin of the spin Seebeck effect in compensated ferrimagnets

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

https://doi.org/10.1038/ncomms10452

Sign of inverse spin Hall voltages generated by ferromagnetic resonance and temperature gradients in yttrium iron garnet platinum bilayers

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

https://doi.org/10.1088/0022-3727/48/2/025001

Weak itinerant antiferromagnetism in PuIn explored using In nuclear quadrupole resonance

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

https://doi.org/10.1088/0953-8984/26/3/036001

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.

Theory of spin Hall magnetoresistance

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

https://doi.org/10.1103/PhysRevB.87.144411

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.

Spin caloritronics

Bauer, G. E. W.*; Saito, Eiji; Van Wees, B. J.*

Nature Materials, 11(5), p.391 - 399, 2012/05

https://doi.org/10.1038/nmat3301

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.

Spin Seebeck insulator

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

https://doi.org/10.1038/nmat2856

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 LaYFeO 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 LaYFeO 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.