This is a recording of from the IEEE Magnetics Society, featuring distinguished lecturer Hendrik Ohldag, giving his presentation, "Ultrafast
and Very Small: Discover Nanoscale Magnetism With Picosecond Time Resolution Using X-Rays."
Full abstract:...
This is a recording of from the IEEE Magnetics Society, featuring distinguished lecturer Hendrik Ohldag, giving his
presentation, "Ultrafast and Very Small: Discover Nanoscale Magnetism With Picosecond Time Resolution
Using X-Rays."
Full abstract:
Today's magnetic device technology is based on complex magnetic alloys or multilayers that are patterned
at the nanoscale and operate at gigahertz frequencies. To better understand the behavior of such devices one needs an experimental
approach that is capable of detecting magnetization with nanometer and picosecond sensitivity. In addition, since devices
contain different magnetic elements, a technique is needed that provides element-specific information about not only ferromagnetic
but antiferromagnetic materials as well. Synchrotron based X-ray microscopy provides exactly these capabilities because a
synchrotron produces tunable and fully polarized X-rays with energies between several tens of electron volts up to tens of
kiloelectron volts. The interaction of tunable X-rays with matter is element-specific, allowing us to separately address different
elements in a device. The polarization dependence or dichroism of the X-ray interaction provides a path to measure a ferromagnetic
moment and its orientation or determine the orientation of the spin axis in an antiferromagnet. The wavelength of X-rays is
on the order of nanometers, which enables microscopy with nanometer spatial resolution. And finally, a synchrotron is a pulsed
X-ray source, with a pulse length of tens of picoseconds, which enables us to study magnetization dynamics with a time resolution
given by the X-ray pulse length in a pump-probe fashion. The goal of this talk is to present an introduction to the field
and explain the capabilities of synchrotron based X-ray microscopy, which is becoming a tool available at every synchrotron,
to a diverse audience. The general introduction will be followed by a set of examples, depending on the audience, that may
include properties of magnetic materials in rocks and meteorites, magnetic inclusions in magnetic oxides, interfacial magnetism
in magnetic multilayers, and dynamics of nanostructured devices due to field and current pulses and microwave excitations.