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We develop a more general methodology for a dual photoelastic modulator (PEM) system that is used for the determination of the Stokes parameters of an arbitrary light beam. This allows for a degree of arbitrariness in the setting of the retardation amplitudes of both PEMs, thus permitting a robust and effective optimization of the detection system. Various experimental issues are considered and a calibration procedure is described that ensures accurate measurement of the absolute values of the Stokes parameters. Measurements of the Faraday rotation of a CoPt multilayer film are provided as a demonstration of the sensitivity of the dual-PEM system. OCIS codes: 120.2130, 230.3810.

We derive a generalized theory of a dual photoelastic modulator system designed for the measurement of the Stokes parameters of an arbitrary light beam. Based on the theory, a critique of various potential configurations that could be used to effect such measurements is presented. A calibration procedure for the entire optical system is introduced which, among other things, renders a knowledge of the frequency response of the detector system unnecessary. An analysis of the errors due to incorrect setting of optical components is presented for some of the more practical cases. This allows an assessment of the relative merit of different experimental configurations. [ABSTRACT FROM AUTHOR]

Cobalt nanowire arrays have been grown onto anodic aluminum oxide templates by using a pulse dc electrodeposition technique. We demonstrate that the crystal structure, grain size, and related magnetic properties can be controlled by applying different pulse frequencies. For a pulse frequency of 25 Hz, monocrystalline hexagonal-close-packed Co nanowires are formed with a well defined [1010] growth axis along the wire length. At a higher pulse frequency of 1000 Hz, face-centered-cubic Co nanowires are deposited with a small grain size and a preferred [111] texture directed along the length of the wire. Possible mechanisms for the observed growth characterization are discussed. An investigation of the corresponding magnetic properties indicates that the fcc Co nanowire arrays have the larger coercivity and squareness values: reasons for this behavior are explored. [ABSTRACT FROM AUTHOR]

We report in this paper a generalized theory that describes the interaction between a monochromatic light beam and an optical system that includes one photoelastic modulator, one analyzer, and one photodetector. Based on the theory, a detailed four-step procedure is presented, which allows a precise measurement of the four Stokes parameters. An analysis of the systematic and random errors arising from the four-step measurements is also given as well as a calibration procedure that involves the use of a general retardation plate. As a practical application the procedure is used to analyze the magneto-optical properties of magnetic thin films grown on GaAs(001) substrates. [ABSTRACT FROM AUTHOR]

The magneto-optical (MO) properties of highly ordered arrays of electrodeposited Co96Pt4 alloy nanowires embedded in anodic aluminum oxide (AAO) membranes have been studied as a function of annealing temperature (TA). The initial measurements yielded the four Stokes parameters from which the Faraday rotation angle (FRA) and ellipticity (tan x) were extracted. The FRA was determined as 8.0x103 deg/cm for the as-deposited sample. After annealing at 300 °C the FRA attained a maximum of 1.1x104 deg/cm san increase of 38%d, but thereafter declined monotonically as TA was increased to 650 °C. The ellipticity shows a similar behavior with TA. However, the corresponding variation in saturation magnetization (Ms) with TA does not match that of the magneto-optical constants, which suggests that factors other than Ms also determine the values of FRA and tan x. The data obtained indicate that a suitable annealing regime is an effective method to optimize the MO properties of AAO-based magnetic nanowire arrays. [ABSTRACT FROM AUTHOR]

The effects of annealing on the crystal structure and magnetic properties of Co-rich cobalt platinum nanowire arrays embedded in anodic aluminium oxide membranes have been investigated. For this purpose, a rapid thermal annealing to temperatures of 300 °C to 800 °C has been used. Transmission electron microscopy and scanning electron microscopy show that the nanowires have a mean diameter of 14 nm and an estimated wire density of 7.8×1010 cm-2. From x-ray diffraction patterns, we find that the nanowires are hcp and possess a preferred texture in which the c axis of the grains tends to lie along the major axis of the wire. Vibrating sample magnetometry measurements indicate that the easy axis is along the nanowire axis direction. Hysteresis loops, saturation magnetization, squareness ratio (Mr/Ms), and coercivity (perpendicular and parallel to the nanowire axis) have all been investigated as a function of the annealing temperature (TA). Coercivity parallel to the wire axis first increases with TA, attains a maximum at 600 °C (which is 150% of the as-deposited sample), and then decreases. By contrast there is relatively little change in the coercivity measured perpendicular to the wires. The saturation magnetization for the as-deposited sample is 1360 emu/cc and remains almost constant for annealing temperatures up to 500 °C: for TA>500 °C it decreases significantly. The maximum (Mr/Ms) ratio attained in this study is 0.99, the highest value reported thus far for cobalt platinum alloy nanowires. The data suggest that these materials are potential candidates for high-density magnetic recording media. [ABSTRACT FROM AUTHOR]

The development of a generalized theory of a dual photoelastic modulator system to measure the stoke parameters of an arbitrary light beam is presented. The system helps to analyze the errors in calibration procedure due to incorrect setting of optical components.

The microstructural properties and corresponding magnetic behavior of Cobalt (Co) nanowires prepared by a pulse dc electrodeposition technique is studied. It is found that the microstructural properties can be controlled by applying different pulse frequencies and the corresponding magnetic properties indicate that the fcc Co nanowire arrays have larger coercivity and squareness values.

The structural and magnetic properties of [Co.sub.1-x][Pt.sub.x] (0.09 less than or equal to x less than or equal to 0.86) nanowire arrays, including the coercivity, squareness, and saturation magnetization are studied as a function of the composition. The crystal structure of the nanowire arrays is found to change progressively from hcp to a mixture of hcp and fcc phases and finally to pure fcc with increasing platinum content.

A study on the magneto-optical (MO) properties of highly ordered arrays of electrodeposited Co(sub 96)Pt(sub 4) alloy nanowires embedded in anodic aluminum oxide (AAO) membranes is carried out as function of annealing temperature [T(sub A)]. The results indicate that a suitable annealing regime is an effective method to optimize the MO properties of AAO-based magnetic nanowire arrays.

Highly ordered 14 nm diam cobalt platinum alloy nanowire arrays with Pt content ranging from 9 to 86 at. % have been electrodeposited into nanoporous anodic aluminum oxide templates. The crystal structure of the as-deposited Co1-xPtx nanowire arrays changes progressively from hcp to a mixture of hcp and fcc phases and finally to pure fcc with increasing Pt content. The coercivity, squareness, and saturation magnetization of the as-deposited nanowire arrays have been investigated as a function of nanowire composition. [ABSTRACT FROM AUTHOR]

We have investigated the growth of Ni–Zn alloys by a dc electrodeposition method and a pulse dc electrodeposition method with different pulse frequencies, under otherwise the same growth conditions. Dendritic growth is found in the Ni–Zn alloys produced by pulse dc electrodeposition, whereas such growth is absent in those fabricated by dc electrodeposition. The morphology of the as-grown Ni–Zn dendrites is highly influenced by the pulse frequency. The possible growth mechanism has been discussed. The corresponding magnetic properties are investigated at 5 K using a superconducting quantum interference device. We have observed a clear variation in the magnetisation behaviour as the pulse frequency is changed, which is likely to be attributable to the presence of precipitation of Ni nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: The use of anodic aluminum oxide (AAO) as a reactive template in the fabrication of ordered arrays of spinel ZnAl2O4 nanostructures is demonstrated. This involves the growth of monocrystalline Zn nanowires into an AAO template using a pulse dc electrodeposition technique followed by a heat treatment in air at 800°C. The formation of ZnAl2O4 nanotubes in the solid-state reaction is driven by the Kirkendall effect. In addition, the formation of such ZnAl2O4 nanostructure arrays requires that the molar ratio of ZnO to Al2O3 be less than unity. This corresponds to a ratio of pore radius to half inter-pore separation of 0.63 which serves as a guide to the initial template geometry required for the formation of an array of discrete nanotubes. [ABSTRACT FROM AUTHOR]

We have investigated the magneto-optical properties of highly ordered Co-Pt alloy nanowire arrays embedded in anodic aluminum oxide templates. The magnetic field-dependent Stokes parameters, Faraday rotation angle and ellipticity were investigated by an in-house magneto-optical measurement system. The extracted hysteresis loops are broadly consistent with magnetic hysteresis loops obtained from the vibrating sample magnetometer. The maximum Faraday rotation angle and ellipticity of these samples were examined as a function of nanowire composition. With an increase of platinum content from 9 at.% to 86 at.% in the as-deposited nanowire arrays, the maximum Faraday rotation angle per length decreases linearly from 1.39 x 10(3) degrees/cm to 1.58 x 10(2) degrees/cm. The maximum ellipticity shows a similar behavior with the composition. These linear relationships suggest a dilution model for the magnetic moment in the alloy nanowires. Our results indicate that magneto-optical measurements comprise an effective and sensitive method for monitoring the behavior of AAO-based magnetic nanowire arrays.