Zeitaufgelöste Magnetisierungsmessungen an ferromagnetischen Filmen und Mikrostrukturen (English shop)

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The magnetization dynamics of ferromagnetic thin films and microstructures are
of great interest for the development and optimization of magneto-electronic de-
vices like the magnetic random access memory (MRAM). In the course of this
thesis we performed time- and frequency-resolved measurements on Permalloy
and iron thin films and microstructures:
• Time-resolved measurements using the magneto-optical Kerr effect: Short
magnetic field pulses generated in photoconductive switches were used to
excite the magnetization dynamics. Both stripes and arrays of iron wires
with a width of 1 μm were investigated. Due to the large shape anisotropy,
the ferromagnetic resonance frequency of the iron wires is twice as high as
that of the wider iron stripes. By using twin excitation pulses, we could
control and suppress the time evolution of the magnetization dynamics in
Permalloy stripes.
• Inductive magnetization measurements using a pulsed inductive microwa-
ve magnetometer (PIMM): In a flip-chip experiment, Permalloy thin films
were put on top of a coplanar waveguide and measured inductively. Additio-
nally, the dynamics of microstructures that were lithographically patterned
directly on top of a waveguide was examined.
• Inductive measurements of the ferromagnetic resonance using a vector net-
work analyzer (VNA): The samples analyzed using the PIMM were also
characterized in the frequency domain with the VNA.
The measurements were compared to simulations calculated using a software that
was developed during the course of this thesis. The software uses the macrospin
model to simulate the magnetization dynamics of thin films and microstructures.
Here, all the measurements performed on Permalloy were in excellent agreement
with the simulation, while the measurements on iron showed significant diffe-
rences.