Variational principle for magnetisation dynamics in a temperature gradient
Institute of Condensed Matter Physics, Station 3, Ecole Polytechnique Fédérale de Lausanne - EPFL CH-1015 Lausanne, Switzerland
Received: 11 September 2015
Accepted: 9 October 2015
By applying a variational principle on a magnetic system within the framework of extended irreversible thermodynamics, we find that the presence of a temperature gradient in a ferromagnet leads to a generalisation of the Landau-Lifshitz equation with an additional magnetic induction field proportional to the temperature gradient. This field modulates the damping of the magnetic excitation. It can increase or decrease the damping, depending on the orientation of the magnetisation wave vector with respect to the temperature gradient. This variational approach confirms the existence of the magnetic Seebeck effect which was derived from thermodynamics and provides a quantitative estimate of the strength of this effect.
PACS: 75.76.+j – Spin transport effects / 76.50.+g – Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
© EPLA, 2015