Near-field scanning optical microscopy (NSOM) has been used to image and record domains in thin-film magneto-optic (MO) materials. In the imaging mode, resolution of 30–50 nm has been consistently obtained, whereas in the recording mode, domains down to ∼60 nm have been written reproducibly. Data densities of ∼45 Gbits/in.2 have been achieved, well in excess of current magnetic or MO technologies. A brief analysis of speed and other issues indicates that the technique may represent a viable alternative to these and other methods for anticipated high density data storage needs.
We describe the implementation of a scanning Hall probe microscope of outstanding magnetic field sensitivity (∼0.1 G) and unprecedented spatial resolution (∼0.35 μm) to detect surface magnetic fields at close proximity to a sample. Our microscope combines the advantages of a submicron Hall probe fabricated on a GaAs/Al0.3Ga0.7As heterostructure chip and the scanning tunneling microscopy technique for precise positioning. We demonstrate its usefulness by imaging individual vortices in high Tc La1.85Sr0.15CuO4 films and superconducting networks, and magnetic bubble domains.
Analysis of globally disordered, nonequilibrium "labyrinthine" stripe-domain patterns in thin ferrimagnetic garnet films has revealed a well-defined local structure containing an oblong polygonal plaquette as the fundamental motif. Two types of labyrinths were found: one having topological defects, the other composed of a single, unbranched, meandering line. These patterns emerge when the labyrinthine state is approached either by heating at constant magnetic field or by demagnetizing from saturation at constant temperature. Size and aspect ratios of the oblong polygonal plaquettes prove to be independent of the choice of these two mutually orthogonal trajectories within the phase diagram, which is surprising in view of the different mechanisms and concomitant topological constraints governing the evolution of disorder. The significance of this unique local structure is discussed in the general context of defectmediated melting of two-dimensional stripe phases.
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