Spin Seebeck Effect New Paradigm for energy harvesting Sadamichi - PowerPoint PPT Presentation

JST Japan-Spain Meeting (March 5, 2013) Spin Seebeck Effect New Paradigm for energy harvesting Sadamichi Maekawa Advanced Science Research Center, Japan Atomic science Agency, Tokai, Japan JST Japan-Spain Collaboration : “ Development in Spin Seebeck Devices” Maekawa goup (JAEA), Saitoh group (Tohoku University), Ibarra group (University of Zaragoza).

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 Spin current Charge: e electron Charge current (Current) Both spin current and charge current → Spin-electronics (Spintronics) (usual electronics ← charge current ）

Energy conversion from heat to electricity: • Seebeck effect : electricity Thermopower Thermo-electric material Large Seebeck effect ( Q ) & heat Small Resistivity ( ρ) are required. Seebeck effect was discovered in 1821.

• Galileo: NASA's Spacecraft (Radioisotope battery, Curiosity,… Nuelear battery) Radioisotope Themroelectric Generator • SEIKO THERMIC • CITIZEN ECO-DRIVE THERMO

Thermo-electric materials: Heat→Electricity Heat of car Garbage burning plant Electricity→Heat Refrigerator Thermo-electric materials ： No vibration (no moving part), Easy to miniaturize, Gentle to environment.

Wine Cellar: Panasonic’s product: no vibration

spin-Seebeck effect Electric voltage Electric current flows! “Spin voltage” Spin current: − J J ↑ ↓ Spin current flows!

= Electric current Electric current = + & Spin current = Spin current ASRC Colloquium

Charge current Spin current carried by conduction electrons = + J J J ↑ ↓ e = − J J J ↑ ↓ s

Spin current carried by spin waves

K. Uchida et al.: Nature 455 , 778 (2008) (Saitoh Group, Maekawa Group) Spin Seebeck effect Pt : spin detector (4 mm x100 µ m x10 nm) NiFe : thermo-spin generator (4 mm x6 mm x20 nm) spin Hall effect: E SHE = D ISHE J s × σ magnitude & polarization of J s Lower T end Higher T end

YIG: Insulating ferrimagnet Spin Seebeck effect: A common phenomenon in ferromagnets!! K. Uchida et al.: Nature Mater. 9, 894 (2010).

Thermoelectric module T + ∆ T electric current current electric P N T electric current

Spin Seebeck (thermoelectric) device (NEC, Saitoh Gr. Maekawa Gr.) Kirihara et al., Nature Materials 11, 686 (2012)

Magnetite (Fe 3 O 4 ) Metal-Insulator Transition at 120K! P. Weiss and R. Forrer, Ann. Phys. 12 , 279(1929) R. W. Millar, J. Am. Chem. Soc. 51 , 215(1929) Metal insulato r Magnetite thin films Developed by U. of T. Okamura, Sci. Rep. Tohoku Imp. Univ. 21 , 231(1932) 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!!