arXiv subjects

Yuki Shiomi

Publications and source records attributed to Yuki Shiomi.

21 records · Page 2Linked to original sources

arXiv2015

Critical suppression of spin Seebeck effect by magnetic fields

The longitudinal spin Seebeck effect (LSSE) in Pt/Y$_3$Fe$_5$O$_{12}$ (YIG) junction systems has been investigated at various magnetic fields and temperatures. We found that the LSSE voltage in a Pt/YIG-slab system is suppressed by applying high magnetic fields and this suppression is critically enhanced at low temperatures. The field-induced suppression of the LSSE in the Pt/YIG-slab system is too large at around room temperature to be explained simply by considering the effect of the Zeeman gap in magnon excitation. This result requires us to introduce magnon-frequency-dependent mechanism into the scenario of LSSE; low-frequency magnons dominantly contribute to the LSSE. The magnetic field dependence of the LSSE voltage was observed to change by changing the thickness of YIG, suggesting that the thermo-spin conversion by the low-frequency magnons is suppressed in thin YIG films due to the long characteristic lengths of such magnons.

cond-mat.mtrl-sci↗

arXiv2015

Generation of Spin Currents in the Skyrmion Phase of a Helimagnetic Insulator $\mathrm{Cu_2OSeO_3}$

We report spin-current generation related with skyrmion dynamics resonantly excited by a microwave in a helimagnetic insulator $\mathrm{Cu_2OSeO_3}$. A Pt layer was fabricated on $\mathrm{Cu_2OSeO_3}$ and voltage in the Pt layer was measured upon magnetic resonance of $\mathrm{Cu_2OSeO_3}$ to electrically detect injected spin currents via the inverse spin Hall effect (ISHE) in Pt. We found that ISHE-induced electromotive forces appear in the skyrmion phase of $\mathrm{Cu_2OSeO_3}$ as well as in the ferrimagnetic phase, which shows that magnetic skyrmions can contribute to the spin pumping effect.

cond-mat.mes-hall↗

arXiv2014

Enhancement of Spin Pumping in $\mathrm{Y_3Fe_5O_{12}/Pt/Ni_{81}Fe_{19}}$ Trilayer Film

We study spin pumping in a $\mathrm{Y_3Fe_5O_{12}(YIG)/Pt/Ni_{81}Fe_{19}(Py)}$ trilayer film by means of the inverse spin Hall effect (ISHE). When the ferromagnets are not excited simultaneously by a microwave, ISHE-induced voltage is of the opposite sign at each ferromagnetic resonance (FMR). The opposite sign is consistent with spin pumping of bilayer films. On the other hand, the voltage is of the same sign at each FMR when both the ferromagnets are excited simultaneously. Futhermore, the voltage greatly increases in magnitude. The observed voltage is unconventional; neither its sign nor magnitude can be expected from spin pumping of bilayer films. Control experiments show that the unconventional voltage is dominantly induced by spin pumping at the Py/Pt interface. Interaction between YIG and Py layers is a possible origin of the unconventional voltage.

cond-mat.mtrl-sci↗