#
APS March Meeting 2016

## Volume 61, Number 2

##
Monday–Friday, March 14–18, 2016;
Baltimore, Maryland

### Session V13: Heat Current Effects on Magnetization Dynamics

2:30 PM–5:30 PM,
Thursday, March 17, 2016

Room: 309

Sponsoring
Units:
GMAG DMP

Chair: Jean-Philippe Ansermet, Ecole Poylytechnique Federale de Lausanne, Switzerland

Abstract ID: BAPS.2016.MAR.V13.5

### Abstract: V13.00005 : Magnetic equivalent of the Seebeck effect.

4:54 PM–5:30 PM

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Abstract

####
Author:

SYLVAIN BRECHET

(EPFL)

Spin
caloritonics seeks to investigate the effect of a thermal gradient on the
electronic charge and spin degrees of freedom. In a conductor, a thermal
gradient leads a transport of the conduction electrons that in turn generate
an electric field along the temperature gradient, which is the well-known
Seebeck effect. In an insulator, there are no conduction electrons. Thus no
electronic charge transport takes place. However, the electronic spins can
reorient themselves in the presence of a temperature gradient as they
precess around an external field oriented along the temperature gradient. In
fact, the temperature gradient generates a magnetic induction field in the
plane orthogonal to the temperature gradient. The effect is the magnetic
analog of the Seebeck effect and is thus refered to as the magnetic Seebeck
effect. It has been observed for the propagation of spin waves along and
against a temperature gradient in a YIG slab. The propagation of spin waves
against the temperature gradient lead to a positive thermal damping and the
propagation along the temperature gradient leads to the opposite effect,
namely a negative thermal damping. Thus, the magnetic Seebeck effect
generate of heat driven spin torque that can generate a positive or a
negative thermal damping. The magnetic Seebeck effect has been recently
established using a fundamental variational approach. In many experimental
situations, the system can be treated as a classical continuum with
magnetisation on the scale of interest where the quantum fluctuations
average out and the underlying microscopic structure is smoothed out. For
the propagation of magnetisation waves in a stationary state, the system is
slightly out of equilibrium but the magnetic kinetic energy is constant. In
such a case, the action of the system is a functional of the magnetisation
and the magnetisation current. Since the magnetisation is a function of the
temperature, the action variation yields an explicit expression for the
magnetic induction field generated by the temperature gradient. This field
lead to a heat driven spin torque that has the same geometry in an insulator
than the spin transfer torque proposed by Berger and Slonczewski in a
conductor.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2016.MAR.V13.5