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Spin Seebeck Effect
JST Japan-Spain Collaboration : “Development in Spin Seebeck Devices” Maekawa goup (JAEA), Saitoh group (Tohoku University), Ibarra group (University of Zaragoza).
JST Japan-Spain Meeting (March 5, 2013)
Sadamichi Maekawa Advanced Science Research Center,
Japan Atomic science Agency, Tokai, Japan
New Paradigm for energy harvesting
JST Japan-Spain Collaboration: “Development in Spin Seebeck Devices” Japanese Team: Maekawa Group (ASRC, JAEA, Tokai): Theory of spin Seebeck effect, Saitoh Group (IMR, Tohoku University, Sendai): Observation of spin Seebeck effect and developmenet in new materials, Spanish Team: Ibarra Group (University of Zaragoza): Development in thin films and devices.
electron
Spin: ±ħ/2
Charge: e
Spin current
Both spin current and charge current → Spin-electronics (Spintronics)
(usual electronics ← charge current)
Electron:
Charge current
(Current)
•Seebeck effect :
heat
electricity T
herm
opow
er
Large Seebeck effect (Q) & Small Resistivity (ρ) are required.
Seebeck effect was discovered in 1821.
Energy conversion from heat to electricity:
Thermo-electric material
•Galileo: NASA's Spacecraft Curiosity,… Radioisotope
Themroelectric Generator
•SEIKO THERMIC •CITIZEN ECO-DRIVE THERMO
(Radioisotope battery, Nuelear battery)
Thermo-electric materials: Heat→Electricity
Electricity→Heat
Thermo-electric materials: No vibration (no moving part), Easy to miniaturize, Gentle to environment.
Garbage burning plant Heat of car
Refrigerator
Wine Cellar: no vibration Panasonic’s product:
spin-Seebeck effect
J J↑ ↓−Spin current:
Electric voltage
“Spin voltage”
Electric current flows!
Spin current flows!
ASRC Colloquium
=
= +
=
Electric current
Electric current &
Spin current
Spin current
Charge current Spin current carried by conduction electrons
eJ J J↑ ↓= +
sJ J J↑ ↓= −
Spin current carried by spin waves
Spin Seebeck effect
Lower T end Higher T end
Pt: spin detector (4 mm x100 µm x10 nm)
NiFe: thermo-spin generator (4 mm x6 mm x20 nm)
spin Hall effect: ESHE = DISHE Js × σ
magnitude & polarization of Js
K. Uchida et al.: Nature 455, 778 (2008) (Saitoh Group, Maekawa Group)
YIG: Insulating ferrimagnet
Spin Seebeck effect: A common phenomenon in ferromagnets!!
K. Uchida et al.: Nature Mater. 9, 894 (2010).
Thermoelectric module
P N
T + ∆T
T
electric current el
ectr
ic
curr
ent electric
current
Spin Seebeck (thermoelectric) device
Kirihara et al., Nature Materials 11, 686 (2012)
(NEC, Saitoh Gr. Maekawa Gr.)
Magnetite (Fe3O4)
P. Weiss and R. Forrer, Ann. Phys. 12, 279(1929)
R. W. Millar, J. Am. Chem. Soc. 51, 215(1929)
T. Okamura, Sci. Rep. Tohoku Imp. Univ. 21, 231(1932)
Metal-Insulator Transition at 120K!
insulator Metal
Magnetite thin films Developed by U. of Zaragoza
R. Ramos et al.: Phys. Rev. B (2013)
JST Japan-Spain Collaboration: “Development in Spin Seebeck Devices” Japanese Team: Maekawa Group (ASRC, JAEA, Tokai): Theory of spin Seebeck effect, Saitoh Group (IMR, Tohoku University, Sendai): Observation of spin Seebeck effect and developmenet in new materials, Spanish Team: Ibarra Group (University of Zaragoza): Development in thin films and devices.
Spin Seebeck devices with magnetite!!