Monday, November 5th, 2012
Western Digital, 1710 Automation Parkway, San Jose, CA
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Cookies, Conversation &
Pizza too at 7:00 P.M.
Presentation at 7:30 P.M.
Spin caloritronics
Pr. Gerrit E.W. Bauer, PhD
Institute of Materials Research, Tohoku University
and
Kavli Institute of NanoScience, TU Delft, The Netherlands
Abstract
The spin degree of freedom of the electron affects not only charge, but
also heat and thermoelectric transport, leading to new effects in small
structures that are studied in the field of spin caloritronics (from
calor, the Latin word for heat).
This lecture addresses the basic physics
of spin caloritronics. Starting with an introduction into thermoelectrics
and Onsager’s reciprocity relations, the generalization to include the
spin dependence in the presence of metallic ferromagnets will be
addressed. Using this foundation I will describe several recently
discovered spin-dependent effects in metallic nanostructures and tunneling
junctions as well as a zoo of spin-related thermal Hall effects in terms
of a two spin-current model of non-interacting electrons (an overview of
the recent literature is given in Ref. 1).
Next, I will argue that
different classes of spin caloritronic effects exists that can be
explained only by the collective spin dynamics in ferromagnets. The
thermal spin transfer torque that allows excitation and switching of the
magnetization in spin valves as well as the operation of nanoscale heat
engines is complemented by thermal spin pumping. The latter generates the
so-called spin Seebeck effect, which is generated by a heat current-
induced non-equilibrium of magnons at a contact between an insulating or
conducting ferromagnet and a normal metal. Under these conditions a net
spin current is injected or extracted from the normal metal that can be
detected by the inverse spin Hall effect.
Both classes can be formulated
by scattering theory of transport in the adiabatic approximation for the
magnetization dynamics and computed in terms of material-dependent
electronic structures. Further issues to be addressed are the relation
between electric, thermal and acoustic actuation, as well as the
application potential of spin caloritronics.
[1] G.E.W. Bauer, in Spin
Currents, edited by S. Maekawa, E. Saitoh, S. Valenzuela and Y. Kimura
(Oxford University Press, in press), arXiv:1107.4395.
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