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!!