Micromagnetic understanding of current-driven domain wall motion in patterned nanowires

¹ CNRS-Université Paris-sud, Physique des solides - Bât. 510, 91405 Orsay, France
² University of Electro-communications - Chofu, 182-8585 Tokyo, Japan
³ Osaka University, Department of Materials Engineering Toyonaka, 560-8531 Osaka, Japan

Received: 27 July 2004
Accepted: 27 January 2005

Abstract

In order to explain recent experiments reporting a motion of magnetic domain walls (DW) in nanowires carrying a current, we propose a modification of the spin transfer torque term in the Landau-Lifchitz-Gilbert equation. We show that it explains, with reasonable parameters, the measured DW velocities as well as the variation of DW propagation field under current. We also introduce coercivity by considering rough wires. This leads to a finite DW propagation field and finite threshold current for DW propagation, hence we conclude that threshold currents are extrinsic. Some possible models that support this new term are discussed.