Spin Seebeck coefficient enhancement by using Ta₅₀W₅₀ alloy and YIG/Ru interface

Abstract

This paper reports that Ta 50 W 50 alloy has a higher spin Hall angle than that of βW by measuring the spin Seebeck coefficients for Fe 5 Y 3 O 12 (YIG)/Ru/Ta 50 W 50 and YIG/Ru/W systems. The spin Seebeck coefficient increased by inserting Ru, and the YIG/Ru/Ta 50 W 50 system achieved 2.4 times the magnitude of spin Seebeck coefficient of the conventional YIG/ Pt system although Ru and Ta 50 W 50 have spin Hall angles with opposite signs. Ru seems to recover the spin mixing conductance that is decreased by Ta-W oxidation at its interface with YIG. To enhance the spin Seebeck coefficient, materials having a high spin Hall angle can be combined with materials having a high spin mixing conductance.

Broadband Optical Detection Using the Spin Seebeck Effect

“…Using our estimates for ∇T and −∇V ISHE , we calculate a quantity akin to a traditional Seebeck coefficient for S LSSE in this Pt/YIG device: S LSSE = −∇V ISHE /∇T = 60 ± 7.8 nV/K. This estimate is in line with previous measurements of S LSSE in Pt/YIG heterostructures [38,39,48,49], but orders of magnitude below (electrical) Seebeck coefficients found in thermoelectric devices [50,51].…”

“…Unlike previous optical detectors that are fully reliant on charge carriers, the devices we examine here use spin current to produce a voltage response from light. Our measurements of an ultrabroadband and featureless (λ), combined with previous SSE dynamical studies [23,29] and routes for enhancing S LSSE [38,39], suggest the promise of a spin-based optical detector that is competitive with current photovoltage architectures.…”

“…This fundamentally different photodetection process is advantageous because it leverages materials with high absorptivity (e.g., heavy metals) that do not necessarily create easily-recoverable carriers, while avoiding the lossy process of carrier separation, injection, and recovery. Although we note that the magnitude of our measured (λ) remains well below more-optimized, photocarrier-based architectures [35,36], recent work on improving the SSE efficiency [38,39] show that much larger values of (λ) are achievable in spin caloritronic devices.…”

“…Furthermore, we know that this intensity generates a V ISHE of 3.457 µV across the ∼80 µm beam spot size, which is roughly measured by two indium contacts spaced 4. 45 [38,39,48,49], but orders of magnitude below (electrical) Seebeck coefficients found in thermoelectric devices [50,51].…”

Special issue on spin caloritronics

“…After its initial discovery, the scientific emphasis has turned to the engineering of the effect. Here, Yuasa et al [1] report on the YIG/Ru system, while Kirihara et al [2] focus on all-oxide hetero-structures. The diffusion of magnons in bulk magnetic insulators as studied theoretically by Rezende et al [3] (also for antiferromagnets) and Basso et al [4] is an important mechanism affecting spin pumping, the spin Seebeck, and related effects.…”