106 research outputs found
Topological, non topological and instanton droplets driven by spin-transfer torque in materials with perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya Interaction
The interfacial Dzyaloshinskii-Moriya Interaction can modify the topology of
droplets excited by a localized spin-polarized current. Here, we show that, in
addition to the stationary droplet excitations with skyrmion number either one
(topological) or zero (non-topological), there exists, for a fixed current, an
excited mode with a non-stationary time behavior. We call this mode "instanton
droplet", which is characterized by time domain transitions of the skyrmion
number. These transitions are coupled to an emission of incoherent spin-waves
that can be observed in the frequency domain as a source of noise. Our results
are interesting from a fundamental point of view to study spin-wave emissions
due to a topological transition in current-driven systems, and could open the
route for experiments based on magnetoresistance effect for the design of a
further generation of nanoscale microwave oscillators
Excitation of Spin Waves in an In-Plane-Magnetized Ferromagnetic Nanowire Using Voltage-Controlled Magnetic Anisotropy
The authors propose applying a microwave-frequency electric field to a ferromagnetic/dielectric nanowire to excite propagating spin waves in the wire, providing a path to energy-efficient spintronic signal processing. This scenario should not be confused with the ``parallel parametric pumping'' discussed previously, as the mechanism of parametric coupling is completely different: via out-of-plane dynamic magnetization, not precession ellipticity
Ultra-sensitive voltage-controlled skyrmion-based spintronic diode
We have designed a passive spintronic diode based on a single skyrmion
stabilized in a magnetic tunnel junction and studied its dynamics induced by
voltage-controlled anisotropy (VCMA) and Dzyaloshinskii-Moriya interaction
(VDMI). We have demonstrated that the sensitivity (rectified voltage over input
microwave power) with realistic physical parameters and geometry can be larger
than 10 kV/W which is one order of magnitude better than diodes employing a
uniform ferromagnetic state. Our numerical and analytical results on the VCMA
and VDMI-driven resonant excitation of skyrmions beyond the linear regime
reveal a frequency dependence on the amplitude and no efficient parametric
resonance. Skyrmions with a smaller radius produced higher sensitivities,
demonstrating the efficient scalability of skyrmion-based spintronic diodes.
These results pave the way for designing passive ultra-sensitive and energy
efficient skyrmion-based microwave detectors.Comment: 11 pages, 3 figure
Electrical detection of single magnetic skyrmion at room temperature
This paper proposes a protocol for the electrical detection of a magnetic skyrmion via the change of the tunneling magnetoresistive (TMR) signal in a three-terminal device. This approach combines alternating spin-transfer torque from both spin-filtering (due to a perpendicular polarizer) and spin-Hall effect with the TMR signal. Micromagnetic simulations, used to test and verify such working principle, show that there exists a frequency region particularly suitable for this achievement. This result can be at the basis of the design of a TMR based read-out for skyrmion detection, overcoming the difficulties introduced by the thermal drift of the skyrmion once nucleated
Lean Six Sigma: A new approach to the management of patients undergoing prosthetic hip replacement surgery
Rationale, aims and objectives In 2012, health care spending in Italy reached €114.5 billion, accounting for 7.2% of the Gross Domestic Product (GDP) and 14.2% of total public spending. Therefore, reducing waste in health facilities could generate substantial cost savings. The objective of this study is to show that Lean Six Sigma represents an appropriate methodology for the development of a clinical pathway which allows to improve quality and to reduce costs in prosthetic hip replacement surgery. Methods The methodology used for the development of a new clinical pathway was Lean Six Sigma. Problem solving in Lean Six Sigma is the DMAIC (Define, Measure, Analyse, Improve, Control) roadmap, characterized by five operational phases which make possible to reach fixed goals through a rigorous process of defining, measuring, analysing, improving and controlling business problems. Results The following project indicated several variables influencing the inappropriate prolongation of the length of stay for inpatient treatment and corrective actions were performed to improve the effectiveness and efficiency of the process of care. The average length of stay was reduced from 18.9 to 10.6 days (-44%). Conclusion This article shows there is no trade-off between quality and costs: Lean Six Sigma improves quality and, at the same time, reduces costs
Phase locking and frequency doubling in spin-transfer-torque oscillators with two coupled free layers
We report measurements of spin-torque-driven oscillations in magnetic multilayer devices containing two in-plane-oriented free layers designed to have significant coupling between them. They are driven to oscillate by spin-transfer torque from two perpendicularly oriented polarizers. For both measured devices and micromagnetic simulations, we find that the oscillations in the two free layers are phase locked, resulting in a frequency doubling and large output signals. The simulations suggest that the oscillations are due to spatially nonuniform dynamics characterized by coupled large-amplitude motion of the two free layers
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