Reversal modes and reversal times in submicron sized elements for MRAM applications

The switching behavior of submicron sized NiFe nanoelements was calculated using a hybrid finite element/boundary element method. The numerical integr ation of the Gilbert equation of motion reveals the transient states during magnetization reversal under the influence of a constant applied field. Th e reversal mode and the reversal time sensitively depend on the size and th e shape of the elements. The 200 x 100 x 10 nm(3) elements switch well belo w 1 ns for an applied field of 80 kA/m and a Gilbert damping constant alpha = 0.1. The elements reverse by non-uniform rotation. If an external field is applied the magnetization starts to rotate near the ends, followed by th e reversal of the center. This process requires only about 0.1 ns. In what follows, the magnetization component parallel to the field direction shows oscillations. which decay within a time of 0.4 ns. The excitation of spin w aves is caused by the precession of the magnetization around the local effe ctive field. A rapid decay of the oscillations is obtained in elements with slanted ends, where surface charges cause a transverse demagnetizing field . (C) 2000 Elsevier Science B.V. All rights reserved.