FMR in patterned arrays of rectangular nanodots
with different aspect ratios
V.
Golub, A. Vovk, E. Tartakovskaya, A.Danilevich
Institute of
Magnetism NASU and MESU,
Research on
magnetization processes and spin dynamics in magnetic nanoparticles
is of great importantance because of their unique
magnetic properties and potential applications in information technology and
wireless communications. The frequency of operation
of computers and cellphones tends to increase in
order to enhance efficiency of data processing and broaden the frequency band
for wireless telecommunications. Conventional magnetic microwave materials are
insulators, and metals were usually excluded from the microwave applications
because of the high conduction losses. This restriction does not apply to
nanostructures, which are much smaller than the penetration depth of
microwaves. The advantages of the nanostructures of ferromagnetic transition
metals over conventional materials are: larger magnetization and a simpler
technology, which can easily be integrated with the common processes in
semiconductor technology. This work is devoted to the investigation of the
effect of shape anisotropy on microwave absorption to tailor microwave spectra
by designing arrays consisting of stripes or wires with specific aspect ratios.
Patterened arrays of 100 nm thick, 300 nm wide NiFe stripes with different aspect ratios separated by 1 mkm gaps covering the area were fabricated using the
electron beam nanolithography. The
quality of the patterning was tested using scanning field emission microscopy
and atomic force microscopy. The microwave properties of the arrays were measured using X-band
The angular dependence of
the resonant field was determined by the shape anisotropy of the stripes. The resonant field increased from about 800 Oe
to 2400 Oe when the applied field was rotated out of
the easy direction in the plane of the array for the arrays with large aspect
ratios. This effect can be used for engineering microwave properties of
magnetic nanocomposites.