12 research outputs found
Tailoring the magnetodynamic properties of nanomagnets using magnetocrystalline and shape anisotropies
Magnetodynamical properties of nanomagnets are affected by the demagnetizing
fields created by the same nanoelements. In addition, magnetocrystalline
anisotropy produces an effective field that also contributes to the spin
dynamics. In this article we show how the dimensions of magnetic elements can
be used to balance crystalline and shape anisotropies, and that this can be
used to tailor the magnetodynamic properties. We study ferromagnetic ellipses
patterned from a 10 nm thick epitaxial Fe film with dimensions ranging from 50
x 150 nm to 150 x 450 nm. The study combines ferromagnetic resonance (FMR)
spectroscopy with analytical calculations and micromagnetic simulations, and
proves that the dynamical properties can be effectively controlled by changing
the size of the nanomagnets. We also show how edge defects in the samples
influence the magnetization dynamics. Dynamical edge modes localized along the
sample edges are strongly influenced by edge defects, and this needs to be
taken into account in understanding the full FMR spectrumComment: Accepted for publication in Phys. Rev.
Giant and time-dependent magnetocaloric effect in high-spin molecular magnets
We have measured and calculated the magnetocaloric effect in macroscopic
samples of oriented high-spin molecular clusters like Mn12 and Fe8 as a
function of the temperature and both the intensity and the sweeping rate of the
applied magnetic field. We have observed a high magnetic entropy variation
around the blocking temperature of the magnetic moment of molecules and
calculated the shift of the entropy variation and cooling temperature, with the
sweeping rate of the magnetic field.Comment: 10 pages, 3 figure
Thickness and temperature dependence of the magnetodynamic damping of pulsed laser deposited on (111)-oriented SrTi
We have investigated the magnetodynamic properties of
(LSMO) films of thickness 10, 15
and 30 nm grown on (111)-oriented SrTi (STO) substrates by pulsed
laser deposition. Ferromagnetic resonance (FMR) experiments were performed in
the temperature range 100--300 K, and the magnetodynamic damping parameter
was extracted as a function of both film thickness and temperature. We
found that the damping is lowest for the intermediate film thickness of 15 nm
with , where is relatively constant as
a function of temperature well below the Curie temperature of the respective
films.Comment: Accepted for publication in Journal of Magnetism and Magnetic
Material
Magneto-Acoustic Waves in antiferromagnetic CuMnAs excited by Surface Acoustic Waves
Magnetoelastic effects in antiferromagnetic CuMnAs are investigated by
applying dynamic strain in the 0.01% range through surface acoustic waves in
the GaAs substrate. The magnetic state of the CuMnAs/GaAs is characterized by a
multitude of submicron-sized domains which we image by x-ray magnetic linear
dichroism combined with photoemission electron microscopy. Within the explored
strain range, CuMnAs shows magnetoelastic effects in the form of N\'eel vector
waves with micrometer wavelength, which corresponds to an averaged overall
spin-axis rotation up to 2.4 deg driven by the time-dependent strain from the
surface acoustic wave. Measurements at different temperatures indicate a
reduction of the wave amplitude when lowering the temperature. However, no
domain wall motion has been detected on the nanosecond timescal
Giant and time-dependent magnetocaloric effect in high-spin molecular magnets
We have measured and calculated the magnetocaloric effect in macroscopic samples of oriented high-spin molecular clusters like Mn12 and Fe8 as a function of the temperature and both the intensity and the sweeping rate of the applied magnetic field. We have observed a high magnetic entropy variation around the blocking temperature of the magnetic moment of molecules and calculated the shift of the entropy variation and cooling temperature, with the sweeping rate of the magnetic field