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We demonstrate a Josephson junction with a weak link containing two ferromagnets with perpendicular magnetic anisotropy and independent switching fields in which the critical current can be set by the mutual orientation of the two layers. Such pseudospin-valve Josephson junctions are a candidate cryogenic memory in an all superconducting computational scheme. Here, we use Pt/Co/Pt/CoB/Pt as the weak link of the junction with d Co = 0.6 nm , d CoB = 0.3 nm , and d Pt = 5 nm and obtain a 60% change in the critical current for the two magnetization configurations of the pseudospin-valve. Ferromagnets with perpendicular magnetic anisotropy have advantages over magnetization in-plane systems, which have been exclusively considered at this point, as, in principle, the magnetization and magnetic switching of layers in the junction should not affect the in-plane magnetic flux. [ABSTRACT FROM AUTHOR]

Tapered coplanar waveguides with integrated photoconductors were designed, fabricated, and measured, with pulsed transmission results comparing well with High Frequency Structure Simulator simulations which predict increased confinement and electric field concentration in the tapered region. Devices made with titanium/gold metallisation were used to demonstrate transmission and confinement, while the magnetoresistive properties of devices with cobalt/copper multilayers were used to demonstrate the field concentration. In the latter case, a mathematical framework was developed to understand the relationship between tapering effects and the picosecond magnetoresistance response. [ABSTRACT FROM AUTHOR]

We use ferromagnetic resonance to study the current-induced torques in YIG/heavy metal bilayers. YIG samples with thickness varying from 14.8 nm to 80 nm, with the Pt or Ta thin film on top, are measured by applying a microwave current into the heavy metals and measuring the longitudinal DC voltage generated by both spin rectification and spin pumping. From a symmetry analysis of the FMR lineshape and its dependence on YIG thickness, we deduce that the Oersted field dominates over spin-transfer torque in driving magnetization dynamics. [ABSTRACT FROM AUTHOR]

Surface structural effects accompanying the antiferromagnetic-ferromagnetic magnetostructral transition of epitaxial FeRh thin films were investigated by grazing incidence x-ray scattering. Measurement of the film lattice parameters and variation of x-ray incident angles allow observation of the transition character on scales ranging from a few nm to the total through-thickness of the film. Out-of-plane lattice measurements confirm that the ferromagnetic phase nucleates from the surface during the heating process and is retained at the surface below the transition temperature during the cooling process. These results suggest that surface strain relief fosters nucleation of the ferromagnetic phase. [ABSTRACT FROM AUTHOR]

We report low current-density switching of pseudospin valve nanopillars fabricated by a three-dimensional focused ion beam lithography. Simulations using the Landau–Liftshitz–Gilbert equation with Slonczewski spin transfer torque term demonstrate that magnetostatic coupling combined with an in-plane applied field results in a strongly inhomogeneous magnetization, which is close to the point of switching in both parallel and antiparallel configurations and so significantly reduced switching currents are possible. [ABSTRACT FROM AUTHOR]

Single dusting layers of size-selected Co nanoclusters (NCs) of sizes ranging from 1.5–5.5 nm have been deposited by a gas-phase aggregation method in ultrahigh vacuum, and embedded within a NiFe matrix. Magnetic hysteresis loops have been obtained using soft x-ray magnetic circular dichroism, which shows that these Co NCs embedded in NiFe exhibit room temperature ferromagnetism with identical coercivity to the surrounding NiFe film. The strong local exchange field at the interface between NiFe and Co NCs, combined with the magnetic anisotropy of the NiFe film, allows stabilization of NC ferromagnetism which persists to room temperature. [ABSTRACT FROM AUTHOR]

Using a three-dimensional focused ion beam lithography process, we have fabricated nanopillar devices that show spin transfer torque switching at zero external magnetic fields. Under a small in-plane external bias field, a field-dependent peak in the differential resistance versus current is observed similar to that reported in asymmetrical nanopillar devices. This is interpreted as evidence for the low-field excitation of spin waves, which in our case is attributed to a spin-scattering asymmetry enhanced by the IrMn exchange bias layer coupled to a relatively thin CoFe fixed layer. [ABSTRACT FROM AUTHOR]

We have studied the reversal of the bulk and interfacial magnetizations of the free layer of a spin valve using soft x-ray resonant magnetic scattering. By dusting the interface of the NiFe free layer with a few angströms of Co, we were able to distinguish between the interfacial and bulk magnetisms by tuning the x-ray photon energy. We measured hysteresis loops of reflected x-ray intensity at selected points in reciprocal space. We find no difference in the switching fields, showing that in transition metal ferromagnets, the exchange interactions are sufficiently strong to prevent a separate interfacial coercivity from arising. [ABSTRACT FROM AUTHOR]

The authors report on the use of a Co/Pt multilayer, which exhibits strong perpendicular magnetic anisotropy, to magnetostatically imprint a domain pattern onto a 50 Å thick Permalloy layer. Element specific soft x-ray magnetic scattering experiments were then performed so as to be sensitive to the magnetic structure of the Permalloy only. Off-specular magnetic satellite peaks, corresponding to a periodic domain stripe width of 270 nm, were observed, confirmed by magnetic force microscopy and micromagnetic modeling. Thus the authors have exploited the element specificity of soft x-ray scattering to discern the purely magnetic correlations in a structurally flat Permalloy film. [ABSTRACT FROM AUTHOR]

We report the results of soft x-ray resonant magnetic scattering experiments conducted on Co/Ru magnetic multilayers patterned into a reflection grating. Sample magnetization dependent scans of the in-plane wave vector transfer were performed to probe the relationship between the lateral physical and magnetic structures. Different Fourier components were found to dominate the sum and difference of these spectra, corresponding to different lateral wave forms for the structure-structure and structure-magnetism correlations. [ABSTRACT FROM AUTHOR]

We have used a transmission line deposited on a transparent substrate to deliver an optically triggered magnetic field pulse to a spin valve structure deposited upon an opaque substrate. The ensuing ferromagnetic resonance oscillations have been studied in optical pump-probe experiments in which the probe passes through the transmission line substrate. The resonance frequencies have been modeled by solving the Landau-Lifshitz equation and are used in determining the anisotropy, exchange bias, and interlayer coupling parameters of the sample. [ABSTRACT FROM AUTHOR]

The reorientation of antiferromagnetically coupled Co layers comprising the pinned layers of an antiparallel biased spin valve is reported. Initially, the lower Co layer is saturated in the growth field in the deposition chamber, but it reorients as the upper Co layer grows to be thicker than the lower one. We have investigated the nature of this reorientation by ex situ transport measurements and Lorentz microscopy, and found it highly inhomogeneous, leading to a complex in-plane domain pattern. This results in a reduction of the giant magnetoresistance of the spin valves close to the balance point, where the benefits of the antiparallel biasing are greatest. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present evidence from soft x-ray resonant magnetic scattering measurements at the Mn L[sub 3] edge for the existence of a small magnetic moment on the antiferromagnetic IrMn pinning layer in a NiFe/Cu/Co/IrMn spin valve structure. The variation of the signal in an applied magnetic field shows that the moment lies antiparallel to the Co moment. Changes in the Mn L[sub 3] edge signal as the Co moment is rotated into the hard direction are rapid and do not appear to be associated with thermal reordering of the antiferromagnetic domain structure. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have contacted the tip of a scanning tunneling microscope (STM) to a Co/Cu magnetic multilayer to locally measure the giant magnetoresistance (GMR) of the multilayer. Apart from a point-contact GMR, the measured MR also reflects a magnetostriction effect in the STM. The resulting GMR ratios are typically 10%, with occasional ratios up to 60%. We attribute spot-to-spot variations of the ratio to differences in the local structure of the magnetic multilayer. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]