Unidirectional spin-wave heat conveyer

Abstract

When energy is introduced into a region of matter, it heats up and the local temperature increases. This energy spontaneously diffuses away from the heated region. In general, heat should flow from warmer to cooler regions and it is not possible to externally change the direction of heat conduction. Here we show a magnetically controllable heat flow caused by a spin-wave current. The direction of the flow can be switched by applying a magnetic field. When microwave energy is applied to a region of ferrimagnetic Y3Fe5O12, an end of the magnet far from this region is found to be heated in a controlled manner and a negative temperature gradient towards it is formed. This is due to unidirectional energy transfer by the excitation of spin-wave modes without time-reversal symmetry and to the conversion of spin waves into heat. When a Y3Fe5O12 film with low damping coefficients is used, spin waves are observed to emit heat at the sample end up to 10 mm away from the excitation source. The magnetically controlled remote heating we observe is directly applicable to the fabrication of a heat-flow controller.

Si-integrated ultrathin films of phase-pure Y3Fe5O12 (YIG) via novel two-step rapid thermal anneal

“…For example, low damping coefficients lead to long magnon lifetimes that are critical for spin logic and spin current generators [1][2][3][4][5][6][7][8][9][10][11][12]. Current research uses either bulk YIG (polycrystalline, 3-10 µm grains) [13] or epitaxial YIG (on gadolinium gallium garnet) [14][15][16][17].…”

Magnonic topological insulators in antiferromagnets

“…[114] reported the observation of magnon Hall-like effect 8 . Therefore, we can expect that the observations of the magnonic WF law in the topologically trivial bulk AF and the magnonic QSHE (helical edge magnons) in the topological AF are now within experimental reach 80,82,83,[115][116][117] via measurement schemes proposed in Ref. [46].…”

Spin-current injection and detection in κ-(BEDT-TTF)2Cu[N(CN)2]Br

“…3(c) and 3(d)). 31 Figure 3(e) shows that the magnitude of the temperature gradient is proportional to the absorbed microwave power, as the dash line shows the linear least squares fitting of the data. This temperature gradient might induce an electric voltage due to the Seebeck effect in κ-Br with the similar symmetry as the ISHE voltage.…”

“…The magnitude of the electric voltage is one or two orders of magnitude smaller than that in conventional Pt/YIG devices, [27][28][29][30] but is close to that observed in polymer/YIG devices. 10 To establish the ISHE in the κ-Br/YIG sample exclusively, it is important to separate the spin-pumping-induced signal from thermoelectric voltage induced by temperature gradients generated by nonreciprocal surface-spin-wave excitation, 31 since thermoelectric voltage in conductors whose carrier density is low, such as κ-Br, may not be negligibly small. In order to estimate temperature gradient under the FMR/SWR condition, we excited surface spin waves in a 3-mm-length YIG sample by using a microwave of which the power is much higher than that used in the present voltage measurements, and measured temperature images of the YIG surface with an infrared camera (Figs.…”