Magnetization reversal in AFC media

In this paper, we report on a study of magnetization reversal processes in antiferromagnetically coupled media. We describe the reversal in terms of the reversible and irreversible susceptibility that has been measured for the CoCrPtB system of fixed-recording layer thickness and variable-stabilization layer thickness. We rind that very thin stabilization layers do not couple strongly to the recording layer, and that for Mrt greater than 0.11 memu/cm(2), some of the change in magnetization becomes irreversible

Novel sputtering-technology for grain-size control

In this paper, we present a description of a novel high-rate plasma sputtering system that allows the control of grain size in sputtered films. Additionally, the system has the advantage of a better utilization of the target material (around 80% to 90%) by eliminating the race track at the target as in conventional plasma magnetron sputtering systems. The potential and capabilities of this novel plasma sputtering device are demonstrated in this paper by the deposition of a number of different Cr thin films suitable for underlayers in thin-film media and for which we have performed a systematic X-ray and TEM analysis to determine the grain-size histograms, mean grain diameters, and their relationship to the sputtering processes

A MULTIVARIATE ANALYSIS OF FACTORS INFLUENCING FARM MACHINERY PURCHASE DECISIONS

This paper presents a model of the farm management process. The model suggests that certain socioeconomic characteristics of farm managers will influence their decision-making process. Several characteristics are hypothesized an tested using multivariate techniques (multivariate analysis of variance, range tests, and multiple comparisons). The analysis indicates that the soil zone, value of machinery inventory, operator's age, and operator's education influence the importance placed on each of 20 factors. On the basis of the analysis it was concluded that such a model of the farm management process can contribute to an understanding of farm management decisions. In addition, it was concluded that farm managers, farm machinery dealers, and extension agents had significantly different perceptions of the importance of these factors to farm managers. This latter conclusion suggests that more research related to the actual process of decision making is warranted.Farm Management,

Growth rate effects in soft CoFe films

We report on growth rate effects in sputter-deposited CoFe films prepared using high target utilization sputtering technology (HiTUS). We find that the grain structure of these polycrystalline films is closely related to the growth rate. By changing the growth rate, samples were prepared with different grain structure, which in turn had the effect of changing the magnetic properties of the films. We demonstrate control of the coercivity, which varied by a factor of more than ten. This was achieved via grain size control in CoFe films of thickness 20 nm. Furthermore, by employing a two-step sputtering process, in which two extreme growth rates are used sequentially, we were able to tune the saturation magnetization

Activation volumes in CoPtCr-SiO2 perpendicular recording media

CoPtCr-SiO2 perpendicular recording media with varying levels of SiO2 were examined by two different methods to determine the activation volume. The first is based on the sweep-rate dependence of the remanence coercivity using Sharrock's equation. The second is based on the measurement of the fluctuation field from time-dependence data, determined using a magneto-optical Kerr effect (MOKE) magnetometer. The values of V-act measured at the coercivity for both methods are almost the same, with the fluctuation field and activation volumes increasing with the SiO2 content. The difference between V-act and the grain volume measured directly from bright-field TEM images decreases as the SiO2 content increases due to the reduction of intergranular exchange coupling. The experimental results indicate that values of V-act obtained from single- and double-layered media are consistent. It was also found that the coercivity and normalized hysteresis loop slope at coercivity varied with SiO2 content, with the coercivity peaking at 8 at % SiO2 (nearly 26 vol% SiO2)

Determination of activation volumes of reversal in perpendicular media

We discuss a method for the determination of activation volumes of reversal in perpendicular media. This method does not require correction for the self-demagnetizing field normally associated with these media. This is achieved by performing time dependence measurements at a constant level of magnetization. From the difference in time taken for the magnetization to decay to a fixed value at two fields-separated by a small increment DeltaH, the activation volume can be determined. We report data for both CoCrPt alloy films and a multilayer film, typical of those materials under consideration for use as perpendicular media. We find activation volumes that are consistent with the hysteresis curves of the materials. The activation volume scales qualitatively with the exchange coupling. The alloy films have significantly lower activation volumes, implying that they would be capable of supporting a higher data density

Time dependence in perpendicular media with a soft underlayer

In this paper we describe measurements of magnetic viscosity or time dependence in magnetic thin films suitable for use as perpendicular recording media. Generally, such effects cannot be measured using conventional magnetometry techniques due to the presence of a thin (0.1 mum) soft underlayer (SUL) in the media necessary to focus the head field. To achieve our results we have developed an ultrastable MOKE magnetometer, the construction of which is described. This has enabled us to measure nominally identical films with and without the presence of the SUL. We find that the presence of the SUL narrows the energy barrier distribution in the perpendicular film increasing the nucleation field (H-n), reducing the coercivity (H-c) and results in an increase in the squareness of the loop. This in turn results in an increase in the magnitude of the viscosity in the region of the H-c but that the range of fields over which the viscosity occurs is reduced

Monolithic centrifugal microfluidic platform for bacteria capture and concentration, lysis, nucleic-acid amplification, and real-time detection

We report the design, fabrication, and characterization of a polymer centrifugal microfluidic system for the specific detection of bacterial pathogens. This single-cartridge platform integrates bacteria capture and concentration, supernatant solution removal, lysis, and nucleic-acid sequence-based amplification (NASBA) in a single unit. The unit is fabricated using multilayer lamination and consists of five different polymer layers. Bacteria capture and concentration are accomplished by sedimentation in five minutes. Centrifugation forces also drive the subsequent steps. A wax valve is integrated in the cartridge to enable high-speed centrifugation. Oil is used to prevent evaporation during reactions requiring thermal cycling. Device functionality was demonstrated by real-time detection of E. coli from a 200-muL sample

Measurement of the B Semileptonic Branching Fraction with Lepton Tags

We have used the CLEO II detector and 2.06fb^(-1) of ϒ(4S) data to measure the B-meson semileptonic branching fraction. The B→Xeν momentum spectrum was obtained over nearly the full momentum range by using charge and kinematic correlations in events with a high-momentum lepton tag and an additional electron. We find B(B→Xeν) = (10.49±0.17±0.43)%, with overall systematic uncertainties less than those of untagged single-lepton measurements. We use this result to calculate the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element V_(cb) and to set an upper limit on the fraction of ϒ(4S) decays to final states other than BB̅