5 research outputs found
Temperature Dependence of Spin Pumping in Ni81Fe19/NbN Bilayer Thin Films
We present a comprehensive study of broadband spin pumping utilizing the
inverse spin Hall effect phenomena in bilayer samples comprising Ni81Fe19 (15
nm) and NbN (with NbN thickness varying from 20 nm to 140 nm), conducted over a
temperature and frequency range spanning from 300 K to 4 K and 2 GHz to 12 GHz,
respectively. Our investigations reveal a systematic shift in ferromagnetic
resonance fields, amplitude, and line widths as functions of both frequency and
temperature. Notably, we observed a temperature-dependent increase in the spin
Hall angle value, surpassing previously reported values. Furthermore, our
results demonstrate a pronounced temperature dependence in the inverse spin
Hall effect voltage, exhibiting a significant reduction below the Tc. This
reduction in inverse spin Hall effect voltage is accompanied by an increase in
the linewidth of the ferromagnetic resonance mode
Ferromagnetic resonance study of eightfold artificial ferromagnetic quasicrystals
We have performed broadband (10 MHz–18 GHz) and narrowband (9.7 GHz) ferromagnetic resonance (FMR) measurements on permalloy thin films patterned with quasiperiodic Ammann tilings having eightfold rotational symmetry. We observed highly reproducible mode structures in the low-frequency, hysteretic regime in which domain walls and unsaturated magnetization textures exist. A minimum of 10 robust modes were observed in patterned samples, compared to the single uniform mode observed in unpatterned permalloy films. The field dependence and approximate eightfold rotational symmetry of the FMR spectra are in good agreement with micromagnetic simulations that confirm the importance of patterning for controlling static and dynamic magnetic response
Controlled Magnetic Reversal in Permalloy Films Patterned into Artificial Quasicrystals
We have patterned novel Permalloy thin films with quasicrystalline Penrose P2 tilings and measured their dc magnetization and ferromagnetic resonance absorption. Reproducible anomalies in the hysteretic, low-field data signal a series of abrupt transitions between ordered magnetization textures, culminating in a smooth evolution into a saturated state. Micromagnetic simulations compare well to experimental dc hysteresis loops and ferromagnetic resonance spectra and indicate that systematic control of magnetic reversal and domain wall motion can be achieved via tiling design, offering a new paradigm of magnonic quasicrystals
A hybrid polymer/ceramic/semiconductor fabrication platform for high-sensitivity fluid-compatible MEMS devices with sealed integrated electronics
Active microelectromechanical systems can couple the nanomechanical domain
with the electronic domain by integrating electronic sensing and actuation
mechanisms into the micromechanical device. This enables very fast and
sensitive measurements of force, acceleration, or the presence of biological
analytes. In particular, strain sensors integrated onto MEMS cantilevers are
widely used to transduce an applied force to an electrically measurable signal
in applications like atomic force microscopy, mass sensing, or molecular
detection. However, the high Young's moduli of traditional cantilever materials
(silicon or silicon nitride) limit the thickness of the devices, and therefore
the deflection sensitivity that can be obtained for a specific spring constant.
Using softer materials such as polymers as the structural material of the MEMS
device would overcome this problem. However, these materials are incompatible
with high-temperature fabrication processes often required to fabricate high
quality electronic strain sensors. We introduce a pioneering solution that
seamlessly integrates the benefits of polymer MEMS technology with the
remarkable sensitivity of strain sensors, even under high-temperature
deposition conditions. Cantilevers made using this technology are inherently
fluid compatible and have shown up to 6 times lower force noise than their
conventional counterparts. We demonstrate the benefits and versatility of this
polymer/ceramic/semiconductor multi-layer fabrication approach with the
examples of self-sensing AFM cantilevers, and membrane surface stress sensors
for biomolecule detection
Spin dynamics, loop formation and cooperative reversal in artificial quasicrystals with tailored exchange coupling
Abstract Aperiodicity and un-conventional rotational symmetries allow quasicrystalline structures to exhibit unusual physical and functional properties. In magnetism, artificial ferromagnetic quasicrystals exhibited knee anomalies suggesting reprogrammable magnetic properties via non-stochastic switching. However, the decisive roles of short-range exchange and long-range dipolar interactions have not yet been clarified for optimized reconfigurable functionality. We report broadband spin-wave spectroscopy and X-ray photoemission electron microscopy on different quasicrystal lattices consisting of ferromagnetic Ni81Fe19 nanobars arranged on aperiodic Penrose and Ammann tilings with different exchange and dipolar interactions. We imaged the magnetic states of partially reversed quasicrystals and analyzed their configurations in terms of the charge model, geometrical frustration and the formation of flux-closure loops. Only the exchange-coupled lattices are found to show aperiodicity-specific collective phenomena and non-stochastic switching. Both, exchange and dipolarly coupled quasicrystals show magnonic excitations with narrow linewidths in minor loop measurements. Thereby reconfigurable functionalities in spintronics and magnonics become realistic