Observation of longitudinal spin-Seebeck effect in cobalt-ferrite epitaxial thin films

Abstract

The longitudinal spin-Seebeck effect (LSSE) has been investigated in cobalt ferrite (CFO), an exceptionally hard magnetic spinel ferrite. A bilayer of a polycrystalline Pt and an epitaxially-strained CFO(110) exhibiting an in-plane uniaxial anisotropy was prepared by reactive rf sputtering technique. Thermally generated spin voltage in the CFO layer was measured via the inverse spin-Hall effect in the Pt layer. External-magnetic-field (H) dependence of the LSSE voltage (VLSSE) in the Pt/CFO(110) sample with H ∥ [001] was found to exhibit a hysteresis loop with a high squareness ratio and high coercivity, while that with H∥[11̄0] shows a nearly closed loop, reflecting the different anisotropies induced by the epitaxial strain. The magnitude of VLSSE has a linear relationship with the temperature difference (ΔT), giving the relatively large VLSSE /ΔT of about 3 μV/K for CFO(110) which was kept even at zero external field.

Interface-induced phenomena in magnetism

“…9(b). The magnon longitudinal spin Seebeck effect has also been observed in (Mn,Zn)Fe 2 O 4 [Uchida et al ., 2010c], NiFe 2 O 4 [Meier et al ., 2013a], Fe 3 O 4 [Ramos et al ., 2013; Wu et al ., 2015a], BaFe 12 O 19 [Li et al ., 2014b], CoFe 2 O 4 [Niizeki et al ., 2015] and in various garnet ferrites [Uchida et al ., 2013]. More recently it has also been shown that the longitudinal spin Seebeck effect can be observed in paramagnetic [Wu et al ., 2015b] and antiferromagnetic insulators in which some spin polarization is produced by a magnetic field [Seki et al ., 2015; Wu et al ., 2016b; Lin et al ., 2016] or by a ferromagnetic substrate [Prakash et al ., 2016].…”

Unconventional scaling and significant enhancement of the spin Seebeck effect in multilayers

“…The SSE has been experimentally established and observed in ferromagnetic materials: metals [1], semiconductors [6,7], and oxides [8][9][10]. Theoretical models have also been developed [11][12][13][14][15].…”

Thermoelectric performance of spin Seebeck effect in Fe3O4/Pt-based thin film heterostructures

“…The SSE has been observed in a range of ferromagnetic materials: metals, 3 semiconductors, 9,10 and insulators. [11][12][13] Thus, the SSE has been experimentally established as a general transport phenomenon in ferromagnets. Since the discovery of the SSE, the study of the interaction among spin, charge, and heat currents has been strongly Schematic illustrations of (a) the conventional Seebeck effect and (b) the spin Seebeck effect (SSE) with the induced inverse spin Hall effect (ISHE) in a non-magnetic metal attached to a ferromagnetic or ferrimagnetic material.…”