389 research outputs found
Domain wall motion in thin ferromagnetic nanotubes: Analytic results
Dynamics of magnetization domain walls (DWs) in thin ferromagnetic nanotubes subject to weak longitudinal external fields is addressed analytically in the regimes of strong and weak penalization. Exact solutions for the DW profiles and formulas for the DW propagation velocity are derived in both regimes. In particular, the DW speed is shown to depend nonlinearly on the nanotube radius
Magnetic domain walls displacement : automotion vs. spin-transfer torque
The magnetization dynamics equation predicts that a domain wall that changes
structure should undergo a displacement by itself - automotion - due to the
relaxation of the linear momentum that is associated with the wall structure.
We experimentally demonstrate this effect in soft nanostrips,transforming under
spin transfer torque a metastable asymmetric transverse wall into a vortex
wall. Displacements more than three times as large as under spin transfer
torque only are measured for 1~ns pulses. The results are explained by
analytical and numerical micromagnetics. Their relevance to domain wall motion
under spin transfer torque is emphasized
Domain wall structure in magnetic bilayers with perpendicular anisotropy
We study the magnetic domain wall structure in magnetic bilayers (two
ultrathin ferromagnetic layers separated by a non magnetic spacer) with
perpendicular magnetization. Combining magnetic force and ballistic electron
emission microscopies, we are able to reveal the details of the magnetic
structure of the wall with a high spatial accuracy. In these layers, we show
that the classical Bloch wall observed in single layers transforms into
superposed N\'eel walls due to the magnetic coupling between the ferromagnetic
layers. Quantitative agreement with micromagnetic calculations is achieved.Comment: Author adresses AB, SR, JM and AT: Laboratoire de Physique des
Solides, CNRS, Universit\'e Paris Sud, UMR 8502, 91405 Orsay Cedex, France ML
: Laboratoire PMTM, Institut Galil\'ee, CNRS, Universit\'e Paris-13, UPR
9001, 93430 Villetaneuse, Franc
Electrical rectification effect in single domain magnetic microstrips: a micromagnetics-based analysis
Upon passing an a.c. electrical current along magnetic micro- or nanostrips,
the measurement of a d.c. voltage that depends sensitively on current frequency
and applied field has been recently reported by A. Yamaguchi and coworkers. It
was attributed to the excitation of spin waves by the spin transfer torque,
leading to a time-varying anisotropic magnetoresistance and, by mixing of a.c.
current and resistance, to a d.c. voltage. We have performed a quantitative
analysis by micromagnetics, including the spin transfer torque terms considered
usually, of this situation. The signals found from the spin transfer torque
effect are several orders of magnitude below the experimental values, even if a
static inhomogeneity of magnetization (the so-called ripple) is taken into
account. On the other hand, the presence of a small non-zero average Oersted
field is shown to be consistent with the full set of experimental results, both
qualitatively and quantitatively. We examine, quantitatively, several sources
for this average field and point to the contacts to the sample as a likely
origin.Comment: to be published in Journal of Applied Physic
Analytical solution of the equation of motion for a rigid domain wall in a magnetic material with perpendicular anisotropy
This paper reports the solution of the equation of motion for a domain wall
in a magnetic material which exhibits high magneto-crystalline anisotropy.
Starting from the Landau-Lifschitz-Gilbert equation for field-induced motion,
we solve the equation to give an analytical expression, which specifies the
domain wall position as a function of time. Taking parameters from a Co/Pt
multilayer system, we find good quantitative agreement between calculated and
experimentally determined wall velocities, and show that high field uniform
wall motion occurs when wall rigidity is assumed.Comment: 4 pages, 4 figure
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