205 research outputs found
Switching magnetic vortex core by a single nanosecond current pulse
In a ferromagnetic nanodisk, the magnetization tends to swirl around in the
plane of the disk and can point either up or down at the center of this
magnetic vortex. This binary state can be useful for information storage. It is
demonstrated that a single nanosecond current pulse can switch the core
polarity. This method also provides the precise control of the core direction,
which constitutes fundamental technology for realizing a vortex core memory.Comment: 13 pages, 4 figure
Current-driven resonant excitation of magnetic vortex
A magnetic vortex core in a ferromagnetic circular nanodot has a resonance
frequency originating from the confinement of the vortex core. By the
micromagnetic simulation including the spin-transfer torque, we show that the
vortex core can be resonantly excited by an AC (spin-polarized) current through
the dot and that the resonance frequency can be tuned by the dot shape. The
resistance measurement under the AC current successfully detects the resonance
at the frequency consistent with the simulation.Comment: 16 pages, 4 figure
Magnetically Superior and Easy to Handle L10-FePt Nanocrystals
We report a successful synthesis of monodisperse L10-FePt nanocrystals which
are not only superior in magnetism but also easy to handle through being
dispersible in solvents. Thanks to a thick SiO2-coating, the thermal treatment
needed to form the L10 structure can be done even at 900 oC without inducing
coalescence and coarsening. The protecting shell was thereafter removed in a
specific way that enabled us to recover the L10-FePt nanocrystals in a
water-dispersion. The SiO2-coated nanocrystals show a high coercivity of 18.5
kOe at room temperature in spite of their core size of only 6.5 nm in diameter,
and the hysteresis loop of the water-dispersed nanocrystals, which were frozen
under an external field, was almost rectangular indicating that their magnetic
and structural orientation could be attained.Comment: 14 pages, 5 figure
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