Minimal field requirement in precessional magnetization switching

We investigate the minimal field strength in precessional magnetization switching using the Landau-Lifshitz-Gilbert equation in under-critically damped systems. It is shown that precessional switching occurs when localized trajectories in phase space become unlocalized upon application of field pulses. By studying the evolution of the phase space, we obtain the analytical expression of the critical switching field in the limit of small damping for a magnetic object with biaxial anisotropy. We also calculate the switching times for the zero damping situation. We show that applying field along the medium axis is good for both small field and fast switching times.Comment: 6 pages, 7 figure

Current-Driven Magnetic Excitations in Permalloy-Based Multilayer Nanopillars

We study current-driven magnetization switching in nanofabricated Ni84Fe16/Cu/Ni84Fe16 trilayers at 295 K and 4.2 K. The shape of the hysteretic switching diagram at low magnetic field changes from 295 K to 4.2 K. The reversible behavior at higher field involves two phenomena, a threshold current for magnetic excitations closely correlated with the switching current, and a peak in differential resistance characterized by telegraph noise, with average period that decreases exponentially with current and shifts with temperature. We interpret both static and dynamic results at 295 K and 4.2 K in terms of thermal activation over a potential barrier, with a current dependent effective magnetic temperature.Comment: 4 pages, 4 Figure

Characterization of a new polysiloxane-based titanium surface treatment for resin titanium bonding

PURPOSE: To characterize the polysiloxane-coated titanium surface with thermal treatment by XPS and AFM. Such a novel coating might significantly enhance resin bonding. METHODS AND MATERIALS: A layer (2mm) of silicone grease (Dow Corning Co., Michigan, USA) was applied on two titanium plates (Permascand, Ljungaverk, Sweden) followed by a thermal treatment at two temperatures, 800 and 1100 ◦C, respectively. Another titanium plate was surface treated by sandblasting. The atomic composition of titanium surfaces and change of chemical state…postprin

Detecting Spin-Polarized Currents in Ballistic Nanostructures

We demonstrate a mesoscopic spin polarizer/analyzer system that allows the spin polarization of current from a quantum point contact in an in-plane magnetic field to be measured. A transverse focusing geometry is used to couple current from an emitter point contact into a collector point contact. At large in-plane fields, with the point contacts biased to transmit only a single spin (g < e^2/h), the voltage across the collector depends on the spin polarization of the current incident on it. Spin polarizations of greater than 80% are found for both emitter and collector at 300mK and 7T in-plane field.Comment: related papers at http://marcuslab.harvard.ed

Fabrication and Characterization of Co1−xFex Alloy Nanowires

Co1−xFex alloy nanowires with 40 nm diam and x=0–1.0 were fabricated by electrodeposition in nanopores of alumina templates. The crystalline structure of the nanowires is concentration dependent and shows a transition from the cobalt hexagonal-closed-packed structure (hcp) to a face-centered-cubic structure (fcc) in the concentration range

Investigation of Magnetic Interactions in Large Arrays of Magnetic Nanowires

The magnetic interactions in large arrays of ordered magnetic nanowires with 12-48 nm diameter and 55-95 nm spacing were investigated using modified Henkel plots. The measurements for nanowire arrays ac demagnetized with the field applied parallel to the nanowire axis (the easy magnetization axis) indicate that the dominant interaction during the switching process is the magnetostatic coupling between the nanowires. Nevertheless, while the strength of the magnetostatic interactions increases with the magnetic moment associated with the nanowires, the increase is not linear with respect to the volume of the nanowires. Moreover, the dependence of the remanence curves on the field history suggests that even for magnetic nanowire systems with high geometric anisotropy, the magnetic pole structure of the nanowires can be complex. This conclusion is also supported by the field dependence of the initial magnetization curves. (c) 2008 American Institute of Physics