Spin transfer and the role of spin-motive-forces for spin valves and domain walls

The interaction of magnetic domains with electrical currents has potentially far reaching applications for spintronics. The requirements of energy conservation are reflected by spin- (smf) and electro-motive-forces (emf) [1] . For spin-valves and domain walls this smf redistributes the currents between the different possible conduction channels in a manner that significantly modifies the dynamics and introduces magnetic relaxation. Our Berry phase approach to domain walls [1,2] has been extended to spin-valves. The results are consistent with the requirements of angular momentum and energy conservation but differ in a number of important ways from those obtained when the Sloncewski torque transfer term is added to the Landau-Liftshitz equations with either Gilbert or Landau-Liftshitz relaxation [3].\break [1] S. E. Barnes and S. Maekawa: Phys. Rev. Lett. {\bf 98}, 246601 (2007)\break [2] S. E. Barnes and S. Maekawa: Phys. Rev. Lett. {\bf 95}, 107204 (2005).\break [3] See e.g., Concepts in Spin Electronics, ed. by S. Maekawa (Oxford Press, 2006).