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Obtaining an accurate profile of the spatial sensitivity of Hall cross structures is crucial if such devices are to be used to analyze the switching behavior of magnetic nanostructures and determine the switching field distribution of bit patterned media. Here, we have used the anomalous Hall effect to investigate the switching of patterned Co/Pt multilayer magnetic nanoislands, where the Hall cross has been integrated into the Pt seed layer. Using the anomalous Hall output voltage we have observed the magnetic switching of individual islands, allowing the spatial sensitivity across a Hall cross structure to be determined. The experimental results agree well with numerical simulation studies, using a three-dimensional finite element model, and with existing theoretical studies, where the spatial sensitivity of two-dimensional Hall cross structures have been found numerically. [ABSTRACT FROM AUTHOR]

E-beam lithography has been used to pattern a continuous Co/Pt multilayer film with perpendicular anisotropy into circular islands of various sizes down to 25 nm diameter on a 60 nm pitch. High resolution magnetic force microscopy with in situ applied field has been used to directly determine the switching field distribution (SFD) and hysteresis loop of the islands. For the smallest islands, the coercivity is reduced and the width of the SFD is increased, indicating that they would not be well suited to data storage applications. [ABSTRACT FROM AUTHOR]

The morphology and stoichiometry of a model iron oxide magnetic tunneling junction heterostructure has been investigated using x-ray photoemission electron microscopy (X-PEEM) and atomic force microscopy (AFM). AFM data evidence islands of width a few μ m and height 10 nm. X-PEEM data show that two types of iron oxide are present, the islands being Fe3O4(111) and the terraces α-Fe2O3(0001). The Fe3O4(111) islands appear as dark areas in X-PEEM, which is attributed to difference in work function and/or mean free path of the two iron oxide phases. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Spin valves are widely used as magnetic microsensors. Their performance is limited by the presence of noise. In this article, signal and noise responses of microfabricated spin valve sensors are investigated in the linear region and in the nonlinear region close to saturation where peaks in noise output have been reported. The anisotropy of the free layer and the pinned layer are in a cross configuration. The noise of the sensor is of 1/f type at low frequency. The signal-to-noise ratio (SNR) as a function of signal frequency was measured near saturation. It is found that below 300 Hz the SNR increases almost linearly as the signal frequency increases. The variation of SNR with excitation current, measured at different frequencies, is shown. The SNR shows a nonlinear characteristic. At low frequency the increase in signal power is matched by that in noise. The SNR curve at 35 Hz shows a maximum as the current increases. The slope of other curves increases with increasing frequency. We explain these curves in a model with thermal excitation. [ABSTRACT FROM AUTHOR]

Polycrystalline Ni[SUB81]Fe[SUB19] films have been vapor-deposited in a forming field onto a 100-μm-thick borosilicate glass. The free surface and film/substrate interface magnetization has been probed using magneto-optical Kerr effect (MOKE) magnetometry, and bulk measurements have been taken using an alternating gradient force magnetometer. Saturation magnetostriction constants were derived from the strain dependence of the anisotropy field in the MOKE measurements, separating out for the first time free surface and interface effects. The free surface showed a clear uniaxial anisotropy with a low dispersion, while the interface showed a mixture of domain switching and moment rotation. We interpret the data in terms of a gradient in magnetic properties through the sample, and discuss consequences for magnetoresistive heads. [ABSTRACT FROM AUTHOR]

Presents a study concerning Barkhausen transitions in single layer and bilayer thin permalloy films. Illustration of the coil measurement system; Measurement method used; Results.

Presents a study which examined the role of magnetic dipole coupling in multilayers that typically comprised of ferromagnetic material separated by a nonmagnetic metal spacer. Numerical calculations; Results; Discussion and conclusions.

Presents a study that prepared double layer thin films of permalloy with tantalum as a nonmagnetic spacer by electron beam evaporation. Effect of deposition parameters on the magnetic properties of the films; Coercivity of the double layer films; Differences in permalloy grain size and grain orientation exhibited by the x-ray diffraction patterns and scanning tunneling microscopy images of the films.

Presents a study which examined the effects of pinning magnetization with geometrical features in thin permalloy thin film device. Experimental procedure; Numerical predictions; Results.

Presents a study that described a detailed investigation into the magnetic and structural properties of permalloy-tantalum multilayered thin films produced by vacuum evaporation. Use of high-resolution transmission electron microscope; Characteristics of multilayered magnetic thin films; Measurement of the magnetic properties of the thin films.

Presents a study which examined the magnetization distributions in thin film Permalloy strips. Experimental method; Results; Micromagnetic modeling.

Presents an automated vibrating sample magnetometer (VSM) designed to facilitate measurements of the magnetization of conducting samples of different fields and temperatures. Features of the VSM; Description of the coil system used for detecting the magnetic flux of vibrating sample; Schematic diagram of the detection and control system in the VSM.

Microfabrication of graphene devices used in many experimental studies currently relies on the fact that graphene crystallites can be visualized using optical microscopy if prepared on top of Si wafers with a certain thickness of SiO2. The authors study graphene’s visibility and show that it depends strongly on both thickness of SiO2 and light wavelength. They have found that by using monochromatic illumination, graphene can be isolated for any SiO2 thickness, albeit 300 nm (the current standard) and, especially, ≈100 nm are most suitable for its visual detection. By using a Fresnel-law-based model, they quantitatively describe the experimental data. [ABSTRACT FROM AUTHOR]