108,804 research outputs found
Ultrasensitive mechanical detection of magnetic moment using a commercial disk drive write head
Sensitive detection of weak magnetic moments is an essential capability in
many areas of nanoscale science and technology, including nanomagnetism,
quantum readout of spins, and nanoscale magnetic resonance imaging. Here, we
show that the write head of a commercial hard drive may enable significant
advances in nanoscale spin detection. By approaching a sharp diamond tip to
within 5 nm from the pole and measuring the induced diamagnetic moment with a
nanomechanical force transducer, we demonstrate a spin sensitivity of 0.032
Bohr magnetons per root Hz, equivalent to 21 proton magnetic moments. The high
sensitivity is enabled in part by the pole's strong magnetic gradient of up to
28 million Tesla per meter and in part by the absence of non-contact friction
due to the extremely flat writer surface. In addition, we demonstrate
quantitative imaging of the pole field with about 10 nm spatial resolution. We
foresee diverse applications for write heads in experimental condensed matter
physics, especially in spintronics, ultrafast spin manipulation, and mesoscopic
physics.Comment: 21 pages, 6 figure
Patterned ferrimagnetic thin films of spinel ferrites obtained directly by laser irradiation
Some spinel ferrites can be oxidized or transformed at moderate temperatures. Such modifications werecarried out on thin films of mixed cobalt copper ferrites and maghemite, by heating small regions with alow-power laser spot applied for about 100 ns. The very simple laser heating process, which can be donedirectly with a conventional photolithographic machine, made it possible to generate two-dimensionalmagnetization heterogeneities in ferrimagnetic films. Such periodic structures could display the specificproperties of magneto-photonic or magnonic crystals
Halbach arrays at the nanoscale from chiral spin textures
Mallinson's idea that some spin textures in planar magnetic structures could
produce an enhancement of the magnetic flux on one side of the plane at the
expense of the other gave rise to permanent magnet configurations known as
Halbach magnet arrays. Applications range from wiggler magnets in particle
accelerators and free electron lasers, to motors, to magnetic levitation
trains, but exploiting Halbach arrays in micro- or nanoscale spintronics
devices requires solving the problem of fabrication and field metrology below
100 {\mu}m size. In this work we show that a Halbach configuration of moments
can be obtained over areas as small as 1 x 1 {\mu}m^2 in sputtered thin films
with N\'eel-type domain walls of unique domain wall chirality, and we measure
their stray field at a controlled probe-sample distance of 12.0 x 0.5 nm.
Because here chirality is determined by the interfacial Dyzaloshinkii-Moriya
interaction the field attenuation and amplification is an intrinsic property of
this film, allowing for flexibility of design based on an appropriate
definition of magnetic domains. 100 nm-wide skyrmions illustrate the smallest
kind of such structures, for which our measurement of stray magnetic fields and
mapping of the spin structure shows they funnel the field toward one specific
side of the film given by the sign of the Dyzaloshinkii-Moriya interaction
parameter D.Comment: 12 pages, 4 figure
Magnetic domain structure and dynamics in interacting ferromagnetic stacks with perpendicular anisotropy
The time and field dependence of the magnetic domain structure at
magnetization reversal were investigated by Kerr microscopy in interacting
ferromagnetic Co/Pt multilayers with perpendicular anisotropy. Large local
inhomogeneous magnetostatic fields favor mirroring domain structures and domain
decoration by rings of opposite magnetization. The long range nature of these
magnetostatic interactions gives rise to ultra-slow dynamics even in zero
applied field, i.e. it affects the long time domain stability. Due to this
additionnal interaction field, the magnetization reversal under short magnetic
field pulses differs markedly from the well-known slow dynamic behavior.
Namely, in high field, the magnetization of the coupled harder layer has been
observed to reverse more rapidly by domain wall motion than the softer layer
alone.Comment: 42 pages including 17 figures. submitted to JA
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