New Directions in Energy Research or a Magnetic Quirk?

1. New Directions in Energy Research or a Magnetic Quirk? Thomas Seebeck Jean Charles Peltier

2. Superconductors Magnetocaloric Effect Thermoelectric effect Research Interests Waste heat harvesting Superconductors Magnetocaloric Effect Thermoelectric effect Magnetic refrigeration Low loss power transfer http://www.superconductors.org/INdex.htm

3. Superconductivity Courtesy Dr Gaifullin Zero Resistance Magnetic Levitation Applications: MRIs CERN

4. Superconductors at CERN 2008: Magnets quenched at the LHC (CERN), putting back discovery of the ‘Higgs boson’ by approximately a year. http://youtu.be/BEnaEMMAO_s http://press.web.cern.ch/press-releases/2008/10/cern-releases-analysis-lhc-incident

5. Magnetocaloric Effect(Solid State Magnetic Refrigeration) http://www.sseec.eu/Solid_State_Energy_Efficient_Cooling.html

6. Magnetocaloric Effect(Solid State Magnetic Refrigeration) Need to find the right material… http://www.sseec.eu/Solid_State_Energy_Efficient_Cooling.html

7. The Thermoelectric Effect JQ JC Jean Charles Peltier Thomas Seebeck

8. Onsager Reciprocity • Onsager-Thomson: • Onsager reciprocity: Lij=Lji • =Peltier coefficient • S=Seebeck coefficient • K=Thermal conductivity • R=1/σ=electrical resistance=1/σ • Jc = charge current • JQ = heat current • Js= spin current Spin dependant Seebeck effect Lars Onsager received the Nobel prize for Chemistry in 1968 "for the discovery of the reciprocal relations bearing his name, which are fundamental for the thermodynamics of irreversible processes“ 𝜫 Spin dependant Peltier effect

9. Harvesting Heat NASA Mars Rover Powered by plutonium-238 http://mars.jpl.nasa.gov/files/mep/MMRTG_Jan2008.pdf

10. Peltier Cells to Recover Waste Heat Skudderites are a popular TEG material:

11. Limited Thermoelectric Efficiency? • Cost • Efficiency • Figure of merit • Wiedeman Franz Law http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2004 /session4/2004_deer_fairbanks2.pdf

13. Current State of the Art Nanostructuring or bulk engineering to improve ZT Vineiset al., Adv. Mater., 22, 3970-3980 (2010) K. Biswas et al., Nature, 489, 414-418 (2009)

14. The Spin Seebeck Effect Co2MnSi NiFe GaMnAs YIG LaY2Fe5O12 K. Uchida et al., Nature Letters, 455, 778-781 (2008)

15. Onsager Reciprocity • Onsager-Thomson: • Onsager reciprocity: Lij=Lji • =Peltier coefficient • S=Seebeck coefficient • K=Thermal conductivity • R=1/σ=electrical resistance=1/σ • Jc = charge current • JQ = heat current • Js= spin current Spin dependant Seebeck effect Spin dependant Peltier effect

16. 2007 Nobel Prize: Fert and Grϋnberg (GMR) Giant Magneto Resistance (GMR) achieved by thin films magnetised anti-parallel (with respect to each other).

17. Moore’s Law “Number of transistors doubles every 2 years” “Data storage density doubles every 2 years” “Processing power doubles every 2 years” http://www.mooreslaw.org/ GMR Intel Corp.

18. What Exactly is Spintronics? Giant MR Spin Hall effect in PMs Using charge and spin to contain information: Four possible states (qubits). Andreev Reflection Current induced spin polarisation in PMs D. Pesin and A.H. MacDonald, Nature Materials, 11, 409-416 (2012)

19. The Spin Seebeck Effect Transverse spin Seebeck Longitudinal spin Seebeck VISHE VISHE B T T A spin current may flow in an electric insulator

20. Aside: How do You Detect a Spin Current? Spin Hall Effect:Generation of a spin polarised current due to charge current flowing from a paramagnet to a ferromagnet. Inverse Spin Hall Effect: Generation of a voltage – EISHE – due to a spin polarised current. Heavy metals such as Pt are typically very good for detection of Js by generation of EISHE.

21. Aside: Spin Hall Angle Can be thought of as the efficiency with which a spin current, JS is converted to a charger current, JC.

22. Maximising VISHE, Minimising Cost [1] A. Hoffman, IEEE Trans. Magn., 49, 5172 (2013). [2] H.L. Wang et al., arXiv:1307.2648 (2013). [3] M. Gradhandet al., Phys. Rev. B, 81 245109 (2010). [4] A. Fert and P.M. Levy, Phys. Rev. Lett., 106 157208 (2011).

23. Measuring the Spin Seebeck Voltage B

24. The Next Stage?

25. Impact of the Spin Seebeck Effect Energy Materials for energy applications Energy efficiency Energy storage Thermoelectrics Increased figure of merit, ZT Charge transport Reduced fabrication costs Thermal transport Spin transport Information and Communication Technologies Physical Sciences Spintronics Thermal spin transfer torque Spin valves Tunnel junctions Magnetic heat switches Non-CMOS technology Quantum Computing

26. Available PhD project. “As part of the PhD you will be expected to characterise potential spin Seebeck samples using x-ray diffraction, x-ray reflectivity, transport measurements, thermal transport and magnetometry. It is also likely that you will prepare patterned thin films using pulsed laser deposition and physical vapour deposition techniques.” http://homepages.lboro.ac.uk/~phkm2/Phd.htm

27. quBitter Pieter Kok (Sheffield) on Quantum Imaging Dan Browne (UCL) on D-Wave’s “quantum” computer When: 7pm Wed 26 March Where: Swan in the Rushes (upstairs) Target Audience: Part C and above but all welcome (space permitting)