50 research outputs found
Dynamics of Vortices in Superconductors Observed by Electron Waves
Although, in electron microscopy, an object is usually observed by using the intensity of an electron beam transmitted through it, the phase distribution of the electron beam also provides different information about the object. It has been difficult, however, to obtain the phase information because of the low coherence of an electron beam. Recent development of a coherent field emission electron beam and related techniques, such as electron holography, has provided a way to observe microscopic objects and fields by precisely measuring the phase information of an electron beam. It has, for example, become possible to observe the dynamics of individual vortices in superconducting thin films
Quantum physics - Disturbance without the force
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62558/1/452298a.pd
Domain Nucleation and Annihilation in Uniformly Magnetized State under Current Pulses in Narrow Ferromagnetic Wires
We investigate the current-driven magnetization dynamics in narrow Permalloy
wires by means of Lorentz microscopy and electron holography. Current pulses
are found to transform the magnetic structure in the uniformly magnetized state
below the Curie temperature. A variety of magnetic states including reversed
magnetic domains are randomly obtained in low probability. The dynamics of
vortices found in most of observed magnetic states seems to play a key role in
triggering the magnetization reversal.Comment: 11 pages, 3 figures, 1 video, to appear in Japanese Journal of
Applied Physics (Express Letter
Domain walls in (Ga,Mn)As diluted magnetic semiconductor
We report experimental and theoretical studies of magnetic domain walls in an
in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our
high-resolution electron holography technique provides direct images of domain
wall magnetization profiles. The experiments are interpreted based on
microscopic calculations of the micromagnetic parameters and
Landau-Lifshitz-Gilbert simulations. We find that the competition of uniaxial
and biaxial magnetocrystalline anisotropies in the film is directly reflected
in orientation dependent wall widths, ranging from approximately 40 nm to 120
nm. The domain walls are of the N\'eel type and evolve from near-
walls at low-temperatures to large angle [10]-oriented walls and small
angle [110]-oriented walls at higher temperatures.Comment: 5 pages, 4 figure