Spin Seebeck voltage enhancement by Mn system metals insertion at the interface between YIG and nonmagnetic layer

Abstract

The spin Seebeck voltage was successfully increased by IrMn or Mn insertion into the interface Y3Fe5O12 and nonmagnetic Pt and TaW with positive and negative spin Hall angle, respectively. The magnitude of the spin Seebeck coefficient ∣S∣ of the samples with IrMn and Mn were higher than that with Ru insertion, which indicates that the existence of the magnetic moment is important for the spin Seebeck coefficient. Furthermore, ∣S∣ of the samples with IrMn and Mn were higher than oxide antiferromagnetic NiO, which suggests the metallic layer insertion is effective for enlarging ∣S∣ owing to the relatively long spin diffusion length. Since the inserted IrMn and NiO take the paramagnetic states as well as Mn, it is supposed that the spin fluctuation in the paramagnetic insertion layers play an important role in enhancing the spin current.

Giant dynamical electron-magnon coupling in metal-metal-ferromagnetic insulator heterostructure

“…On the other hand, inserting an intermediate material with a higher work function (corresponding to negative v) suppresses the spin conductance. Our result is consistent with experimental results that enhancement between 300% to 600% were achieved when intermediate materials such as Ru [18], monolayer WSe 2 [21], multilayer MoS 2 [23,24], and C 60 [22] are inserted at the Pt-YIG interface [47]. The enhancement has previously been attributed to the reduction of conductivity mismatch at the Pt/YIG interface, i.e., the spin mixing conductance g Pt/YIG is smaller than the total conductance of Pt/X/YIG trilayer [48].…”

“…However, in achieving multi-functionalities, one has to balance among different targeted properties in choosing the suitable material, which makes it difficult to optimize a single property. Efforts have been made to control the quality of interface by avoiding oxidization layer [18], changing surface roughness [19], and surface polishing [20]. Another strategy is to reduce the conductivity mismatch at the interface by inserting another layer of material [17], which is proven to be very successful.…”

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.…”