Thermographic measurements of the spin Peltier effect in metal/yttrium-iron-garnet junction systems

Abstract

The spin Peltier effect (SPE), heat-current generation due to spin-current injection, in various metal (Pt, W, and Au single layers and Pt/Cu bilayer)/ferrimagnetic insulator (yttrium iron garnet: YIG) junction systems has been investigated by means of a lock-in thermography (LIT) method. The SPE is excited by a spin current across the metal/YIG interface, which is generated by applying a charge current to the metallic layer via the spin Hall effect. The LIT method enables the thermal imaging of the SPE free from the Joule-heating contribution. Importantly, we observed spin-current-induced temperature modulation not only in the Pt/YIG and W/YIG systems but also in the Au/YIG and Pt/Cu/YIG systems, excluding the possible contamination by anomalous Ettingshausen effects due to proximity-induced ferromagnetism near the metal/YIG interface. As demonstrated in our previous study, the SPE signals are confined only in the vicinity of the metal/YIG interface; we buttress this conclusion by reducing a spatial blur due to thermal diffusion in an infrared emission layer on the sample surface used for the LIT measurements. We also found that the YIG-thickness dependence of the SPE is similar to that of the spin Seebeck effect measured in the same Pt/YIG sample, implying the reciprocal relation between them.PACS numbers: 72.20. Pa,

Magnetic-field-induced decrease of the spin Peltier effect in Pt/Y3Fe5O12 system at room temperature

“…This value is almost same as the value obtained in the thermographic experiments [17,19]; since in Ref. [19] the sine-wave amplitude A of ∆T SPE is divided by the rectangular-wave amplitude of ∆j c , a correction factor of π/4 is necessary, i.e. ∆T SPE /∆j c = πA/ (4∆j c ) = 3.7 × 10 −13 Km 2 /A in the previous study.…”

“…While (i) is not well experimentally investigated, the existence of the µm-range length scale in the SPE [19] and the similarity between δ SPE and δ SSE suggest the dominant contribution from (ii) as in the case of the SSE [25,30]. In fact, recently, it has been demonstrated that the high magnetic fields reduce the propagation length of magnons contributing to the SSE [30].…”

“…To reveal the mechanism of the SPE, systematic experiments have been conducted [17][18][19]. Since the SPE is driven by magnetic fluctuations (magnons) in the F layer, detailed study on the magnetic-field and temperature dependence is indispensable for clarifying the microscopic relation between the SPE and magnon excitation and the reciprocity between the SPE and SSE [20][21][22][23][24][25][26][27][28][29].…”

Magnon polarons in the spin Peltier effect

“…This process accompanies a heat flow J q between the PM/FI and thereby modulates the system temperature. The SPE-induced temperature modulation ∆T SPE satisfies the following relation [36][37][38]…”

Experimental proof of the reciprocal relation between spin Peltier and spin Seebeck effects in a bulk YIG/Pt bilayer

“…Although experimental evidence of both effects has been already obtained [16,17], the quantitative demonstration of their reciprocity, the relation between the two effects and the connection with intrinsic properties of the layers, has yet to be proven [13,18,19,20].…”