Unconventional domain wall magnetoresistance of patterned Ni/Nb bilayer structures below superconducting transition temperature of Nb.

Scattering of spin-up and spin-down electrons while passing through a ferromagnetic domain wall (DW) leads to an additional resistance for transport current, usually observed prominently in constricted magnetic structures. In this report we use the resistance of the DW as a probe to find an indirect signatures of the theoretically predicted spin-singlet supercurrent to spin-triplet supercurrent conversion effect of ferromagnetic DWs. Here we examine the DW induced resistance in Ni stripe in a bilayer Ni/Nb geometry in the normal state and in the superconducting state of Nb.

Nanoscale Domain Wall Engineered Spin-Triplet Josephson Junctions and SQUID.

Spin-singlet Cooper pairs convert to spin-triplet Cooper pairs on passing through a magnetically noncollinear structure at a superconductor(S)/ferromagnet(F) interface. In this context, the generation of triplet supercurrents through intrinsic ferromagnetic domain walls, which are naturally occurring noncollinear magnetic features, was proposed theoretically in the past decade. However, an experimental demonstration has been lacking in the literature, particularly because of the difficulty in accessing a single domain wall, which is typically buried between two domains in a ferromagnetic material.

Exchange-bias nanosegregation in novel Fe Mn Al ( = -0.25, 0, 0.25) Heusler films.

Exchange-bias has been reported in bulk nanocrystalline FeMnAl, but individual thin films of this Heusler alloy have never been studied so far. Here we study the structural and magnetic properties of nanocrystalline thin films of Fe Mn Al ( = -0.25, 0 and 0.

Superconducting exchange coupling between ferromagnets.

Recent discoveries from superconductor (S)/ferromagnet (FM) heterostructures include π-junctions, triplet pairing, critical temperature (T) control in FM/S/FM superconducting spin valves (SSVs) and critical current control in S/FM/N/FM/S spin valve Josephson junctions (N: normal metal). In all cases, the magnetic state of the device, generally set by the applied field, controls the superconducting response. We report here the observation of the converse effect, that is, direct superconducting control of the magnetic state in GdN/Nb/GdN SSVs.

In Situ Observations of Phase Transitions in Metastable Nickel (Carbide)/Carbon Nanocomposites.

Nanocomposite thin films comprised of metastable metal carbides in a carbon matrix have a wide variety of applications ranging from hard coatings to magnetics and energy storage and conversion. While their deposition using nonequilibrium techniques is established, the understanding of the dynamic evolution of such metastable nanocomposites under thermal equilibrium conditions at elevated temperatures during processing and during device operation remains limited. Here, we investigate sputter-deposited nanocomposites of metastable nickel carbide (NiC) nanocrystals in an amorphous carbon (a-C) matrix thermal postdeposition processing via complementary in situ X-ray diffractometry, in situ Raman spectroscopy, and in situ X-ray photoelectron spectroscopy.

Nano-optical single-photon response mapping of waveguide integrated molybdenum silicide (MoSi) superconducting nanowires.

We present low temperature nano-optical characterization of a silicon-on-insulator (SOI) waveguide integrated SNSPD. The SNSPD is fabricated from an amorphous MoSi thin film chosen to give excellent substrate conformity. At 350 mK, the SNSPD exhibits a uniform photoresponse under perpendicular illumination, corresponding to a maximum system detection efficiency of approximately 5% at 1550 nm wavelength.

Pure second harmonic current-phase relation in spin-filter Josephson junctions.

Higher harmonics in current-phase relations of Josephson Junctions are predicted to be observed when the first harmonic is suppressed. Conventional theoretical models predict higher harmonics to be extremely sensitive to changes in barrier thickness, temperature, and so on. Here we report experiments with Josephson junctions incorporating a spin-dependent tunnelling barrier, revealing a current-phase relation for highly spin polarized barriers that is purely second harmonic in nature and is insensitive to changes in barrier thickness.

Electric-field-dependent spin polarization in GdN spin filter tunnel junctions.

Tunnel junctions incorporating GdN ferromagnetic semiconductor barriers show a spin polarization exceeding 90% and a high conductance. These devices show an unusual low-bias conductance peak arising from a strong bias-dependence of the spin polarization. This originates from a strong magneto-electric coupling within a double Schottky barrier formed with the NbN electrodes.

A superconducting nanowire single photon detector on lithium niobate.

Superconducting nanowire single photon detectors (SNSPDs) are a key enabling technology for optical quantum information science. In this paper we demonstrate a SNSPD fabricated on lithium niobate, an important material for high speed integrated photonic circuits. We report a system detection efficiency of 0.

Vertically oriented TiO(x)N(y) nanopillar arrays with embedded Ag nanoparticles for visible-light photocatalysis.

We present a straightforward method to produce highly crystalline, vertically oriented TiO(x)N(y) nanopillars (up to 1 μm in length) with a band gap in the visible-light region. This process starts with reactive dc sputtering to produce a TiN porous film, followed by a simple oxidation process at elevated temperatures in oxygen or air. By controlling the oxidation conditions, the band gap of the prepared TiO(x)N(y) can be tuned to different wavelength within the range of visible light.

Spin-filter Josephson junctions.

Josephson junctions with ferromagnetic barriers have been intensively investigated in recent years. Of particular interest has been the realization of so called π-junctions with a built-in phase difference, and induced triplet pairing. Such experiments have so far been limited to systems containing metallic ferromagnets.

Magnetic exchange hardening in polycrystalline GdN thin films.

We report the observation of intrinsic exchange hardening in polycrystalline GdN thin films grown at room temperature by magnetron sputtering. We find, in addition to the ferromagnetic phase, that a fraction of GdN crystallizes in a structural polymorphic form which orders antiferromagnetically. The relative fraction of these two phases was controlled by varying the relative abundance of reactive species in the sputtering plasma by means of the sputtering power and N(2) partial pressure.

In-situ observation of transition between surface relief and wrinkling in thin film shape memory alloys.

Significant surface morphology evolution between relief and wrinkling was observed on a 3.5 microm thick TiNiCu film sputter-deposited on a silicon substrate. At room temperature, variation in surface relief morphology (from separated martensite crystals embedded in amorphous matrix to fully interweaved martensite plates) was observed with slight change in film composition.

Silicon-substituted hydroxyapatite thin films: effect of annealing temperature on coating stability and bioactivity.

The effect of annealing temperature on the physicochemical and biological characteristics of magnetron cosputtered silicon-substituted hydroxyapatite (SiHA) thin coatings was studied. Annealing is required to transform as-sputtered amorphous films into crystalline coatings. A nanocrystalline, single-phase apatite structure was achieved for coatings heated to 600 or 700 degrees C and, with increasing annealing temperature, the crystallite size increased.

The response of osteoblasts to nanocrystalline silicon-substituted hydroxyapatite thin films.

Magnetron co-sputtering has been employed to fabricate thin nanocrystalline coatings of silicon-substituted hydroxyapatite (SiHA) of different Si compositions: 0.8 wt%, 2.2 wt%, and 4.

Novel silicon-doped hydroxyapatite (Si-HA) for biomedical coatings: an in vitro study using acellular simulated body fluid.

Magnetron co-sputtering was used to produce silicon-doped hydroxyapatite (Si-HA) as coatings intended for potential applications such as orthopedic and dental implants. It was found that the crystallinity of the as-sputtered coatings increased after annealing, resulting in a nanocrystalline apatite structure. Subsequently, the bioactivity of the coatings was evaluated in an acellular simulated body fluid (SBF).

A new way of incorporating silicon in hydroxyapatite (Si-HA) as thin films.

Bioactive silicon-containing hydroxyapatite (Si-HA) thin films that can be used as coatings for bone tissue replacement have been developed. A magnetron co-sputtering technique was used to deposit Si-HA films up to 700 nm thick on titanium substrates, with a silicon level up to 1.2 wt%.

Magnetron co-sputtered silicon-containing hydroxyapatite thin films--an in vitro study.

The use of silicon-substituted hydroxyapatite (Si-HA) as a biomaterial has been reported recently. In vivo testing has shown that Si-HA promotes early bonding of the bone/implant interface. In order to extend its usage to major load-bearing applications such as artificial hip replacement implants, it has been proposed that the material could be used in the form of a coating on implant surfaces.

Critical current of YBa(2)Cu(3)O(7-delta) low-angle grain boundaries.

Transport critical current measurements have been performed on 5 degrees [001]-tilt thin film YBa(2)Cu(3)O(7-delta) single grain boundaries with the magnetic field rotated in the plane of the film, phi. The variation of the critical current has been determined as a function of the angle between the magnetic field and the grain boundary plane. In applied fields above 1 T the critical current j(c) is found to be strongly suppressed only when the magnetic field is within an angle phi(k) of the grain boundary.

Coated silica tips for use in high-pressure, high-temperature, scanning tunneling microscopy.

A novel application of coated silica tips for use in high-pressure, high-temperature, scanning tunneling microscopy is introduced. Thermal drift is reduced in the Z-direction due to the low thermal expansion of silica. Virtually, any conducting material that can be evaporated or sputtered can be used as a tip material.

Effects of interlayer coupling on the irreversibility lines of NbN/AlN superconducting multilayers.

We have studied the temperature dependence of the in-plane resistivity of NbN/AlN multilayer samples with varying insulating layer thickness in magnetic fields up to 7 T parallel and perpendicular to the films. The upper critical field shows a crossover from 2D to 3D behavior in parallel fields. The irreversibility lines have the form (1-T/T(c))(alpha), where alpha varies from 4 / 3 to 2 with increasing anisotropy.