Lorentz microscopy studies of domain wall trap structures

Abstract

Vortex domain wall chirality rectification due to the interaction with end domain spin structures in permalloy nanowires Appl. Phys. Lett. 95, 252501 (2009); 10.1063/1.3275576 The effect of geometrical confinement and chirality on domain wall pinning behavior in planar nanowires J. Appl. Phys. Domain wall trapping probed by magnetoresistance and magnetic force microscopy in submicron ferromagnetic wire structures J. Appl. Phys. 85, 6178 (1999); 10.1063/1.370213Lorentz microscopy of small magnetic structures (invited) Domain wall traps of varying geometry have been studied using Lorentz microscopy in a transmission electron microscope. Electron beam lithography and lift-off were used to fabricate the elements whose shape allowed the formation of a head-to-head domain structure in the central section. Previous micromagnetic simulations have shown that different head-to-head configurations are possible depending on the width and thickness of the strip. In the majority of our in situ magnetizing experiments a vortex domain wall configuration was nucleated. This could be moved reproducibly between the ends of the element under fields of a few tens of oersted.

Tuning the magnetization reversal process of FeCoCu nanowire arrays by thermal annealing

“…The coercivity value for the transverse wall reversal mode is known to be always larger than that for the vortex wall mode, [25][26][27][28] and thus, during the transition between the two DW types, the coercivity increases. Consequently, the experimentally observed enhanced coercivity after annealing can be understood in terms of the transition between VDW propagation for as prepared nanowires and TDW propagation for the annealed nanowires.…”

Controlled domain wall injection into ferromagnetic nanowires from an optimized pad geometry

“…Thus, the pad vortex remained intact at the end of each complete injection/propagation cycle. Figure 3 shows Fresnel images 16 illustrating the processes described above. Here, magnetic contrast arises at the positions of DWs and also at film edges where M generally lies parallel to the edge.…”

“…7,10,13,16 The alternative approach, adopted here, is to attach a larger dimension pad to a straight ferromagnetic nanowire, in which case injection and propagation can be achieved using only single-axis magnetic fields parallel to the wire axis. 3,5,17 This is advantageous when the application of vector magnetic fields is impractical.…”

Observation of field-induced domain wall propagation in magnetic nanowires by magnetic transmission x-ray microscopy

“…Lorentz-transmission electron microscopy, 16,17 also performed in vacuum, requires samples to be on electron-transparent substrates and of a minimum thickness (typically 20 nm for Ni 81 Fe 19 ) but nevertheless can produce excellent images of domain wall structure in magnetic nanowires. 17 Finally, magnetic transmission X-ray microscopy (M-TXM) 18,19 can produce in-field magnetization images from samples in air, although X-ray-transparent substrates (similar to those in Lorentz TEM) must again be used.…”