Lecture Jean-Paul Adam
|02 maart 2009||FWN-Building 5116.0215, Nijenborgh 4, 9747 AG, Groningen|
|Speaker:||Dr. Jean-Paul Adam|
Laboratoire de Physique des Solides,
Université Paris-Sud XI, Orsay Cedex
|Title:||Current and field induced domain wall motion in a GaMnAs track|
|Date:||Mon Mar 2, 2009|
|Host:||Bart van Wees|
|Telephone:||+31 50 363 4933|
A spin polarised current can exert torques on a domain wall inducing a displacement of this domain wall. When considering only adiabatic spin torque, domain walls can move only at current densities higher than intrinsic threshold, jc. The wall displacement implies a continuous deformation of the internal domain wall structure. A non-adiabatic spin torque, characterised by the so-called beta parameter, allows wall motion at lower current densities than jc. Previous experiments shown an easy domain wall motion in GaMnAs tracks and a beta parameter equal to 0 was deduced from creep analysis [1,2].
We will focus on the current and field induced domain wall motion in a 90 micron long and 4 micron wide track made out of a 50 nm thick perpendicular magnetic anisotropy epitaxial GaMnAs layer, grown on GaInAs buffer layer. As expected in the presence of intrinsic pinning defects, the domain wall velocity exhibits a creep regime. Despite low current thresholds, the available range of velocity below the depinning regime is too small to deduce an unambiguous value of critical dynamic exponent and to determine the involved spin transfer torque mechanism. In our perpendicularly magnetised track, two domain walls can be introduced to form a domain of limited size. The domain size can be strongly modified under very weak magnetic field but assisted by current. The current assisted depinning of the wall under weak magnetic field will be discussed to understand and study the intrinsic mechanism of domain wall motion under both magnetic field and spin polarised current.
|Laatst gewijzigd:||22 oktober 2012 14:30|