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

Tomohiko Niizeki; Takashi Kikkawa; Ken Ichi Uchida; Mineto Oka; Kazuya Z. Suzuki; Hideto Yanagihara; Eiji Kita; Eiji Saitoh

doi:10.1063/1.4916978

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

Tomohiko Niizeki, Takashi Kikkawa, Ken Ichi Uchida, Mineto Oka, Kazuya Z. Suzuki, Hideto Yanagihara, Eiji Kita, Eiji Saitoh

IMR - Integrated Research Division

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36 Citations (Scopus)

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 (V_LSSE) 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 || [1 1 0] shows a nearly closed loop, reflecting the different anisotropies induced by the epitaxial strain. The magnitude of V_LSSE has a linear relationship with the temperature difference (ΔT), giving the relatively large V_LSSE /ΔT of about 3 μV/K for CFO(110) which was kept even at zero external field.

Original language	English
Article number	053603
Journal	AIP Advances
Volume	5
Issue number	5
DOIs	https://doi.org/10.1063/1.4916978
Publication status	Published - 2015 May 1

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title = "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 || [1 1 0] 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.",

author = "Tomohiko Niizeki and Takashi Kikkawa and Uchida, {Ken Ichi} and Mineto Oka and Suzuki, {Kazuya Z.} and Hideto Yanagihara and Eiji Kita and Eiji Saitoh",

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AU - Niizeki, Tomohiko

AU - Kikkawa, Takashi

AU - Uchida, Ken Ichi

AU - Oka, Mineto

AU - Suzuki, Kazuya Z.

AU - Yanagihara, Hideto

AU - Kita, Eiji

AU - Saitoh, Eiji

PY - 2015/5/1

Y1 - 2015/5/1

N2 - 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 || [1 1 0] 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.

AB - 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 || [1 1 0] 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.

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

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