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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6384-6386 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In studies of the giant magnetoresistance (GMR) of ferromagnetic/nonmagnetic/ferromagnetic sandwich films, both the anisotropic magnetoresistance (AMR) and the GMR change with the angle between the magnetizations of the individual layers when the current direction is fixed. A technique is presented that separates the two phenomena and shows explicitly the angular dependence of the GMR. The technique relies on layered films in which the magnetization of one or more layers is held fixed by an exchange biasing field and the magnetization of another layer is rotated by an applied field. The separation of the two magnetoresistance contributions takes advantage of the fact that the GMR has a cosine angular dependence and the AMR of the rotated layer has a cosine squared angular dependence. The results indicate the GMR can be isolated from the AMR using only data containing contributions from both.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The anisotropic magnetoresistance (AMR) has been measured at room temperature on a series of epitaxial iron films of various thicknesses. Seven of the films range in thickness from 5 to 20 nm, and one is 500 nm thick. The resistivity of the films was measured with current along photolithographically defined paths parallel to three directions of high symmetry in the single crystal films ([001], [110], and [111]). It was determined that the magnitude of the AMR depends upon the direction the current is applied and that this directional dependence increases with film thickness until saturating near 20 nm. The AMR is roughly 0.15% for all crystal directions in the thinnest films, while in the thickest film, the AMR is 0.08% with current along the [001] direction, 0.35% along the [110] direction, and 0.51% along the [111] direction. These values are to be compared with the AMR of bulk polycrystalline iron which is 0.2%; a weighted average over the different crystallographic directions.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4967-4967 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The extraordinary Hall effect can be used to monitor the magnetization component perpendicular to the plane of a thin film.1 This technique has been used to monitor the time dependence of the magnetization of a series of RE-TM alloys. At room temperature these samples exhibit relatively square hysteresis loop, i.e., the demagnetization effects are minimal. The data are accumulated in the presence of applied magnetic fields approximately equal to the coercive field. The time dependence of the magnetization can be altered by tuning the applied field by only a few percent. Two simple models have been applied to the magnetization process in these films. The first considers the magnetization process in the films if disorder is dominate; then the relaxation of the magnetization would be quasilogrithmic in time. The second is if disorder does not dominate then one might expect an exponential time dependence to be observed. The data have been analyzed in terms of both of these simple models.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5335-5335 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A compact, low noise magnetic force microscope has been constructed. It utilizes an ac interferometric detection scheme sensitive to the magnetic force gradients above a sample. It is similar to the design proposed by Rugar et al.1 A variety of magnetic recording medias, both longitudinal and vertical with written patterns, have been investigated. The studies have been made using etched Ni cantilevers. Contrast and resolution of the microscope as a function of cantilever scan heights will be discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5808-5810 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An optical technique for constant-height mode scanning force microscopy has been developed. This approach allows the sample-tip spacing to be held constant or varied in a quantitative manner during data acquisition. The technique uses an all-fiber interferometric system extended to include two optical cavities: one between the fiber and the cantilever and a second between the fiber and the sample surface. It is necessary that the cantilever be semitransparent or that the fiber be positioned over the edge of the cantilever. It has been experimentally verified that either case allows sufficient laser light for both the cantilever-fiber and the sample-fiber cavities. This method can be used to monitor the time dependence of surface forces, magnetic or electric phase transitions, or as a height calibration for use with scanning force microscopy. As a demonstration of the technique, spatially localized observations of the ferromagnetic phase transition in a gadolinium film are presented. During this observed phase transition, the tip-sample separation was held constant at 1000 nm with a drift of only 3 nm, nominal, for 15 min while the temperature was cycled between 285 and 295 K.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6671-6673 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Both the isothermal remanent magnetization and the dc demagnetization remanence were measured on thin films of CoCr with a perpendicular anisotropy energy suitable for perpendicular recording media. The measurements were made with two applied magnetic field geometries, parallel and perpendicular to the film plane. Plots of the dc demagnetization remanence versus the isothermal remanent magnetization were used to determine the presence of interactions for both applied magnetic field geometries. As expected, the perpendicular magnetization process is dominated by the demagnetization field. When the data are corrected for the demagnetization field, a residual negative interaction is found from the perpendicular data. This negative interaction was also observed in the parallel applied field geometry plots, where the demagnetization factor is negligible. The success of the analysis, using a mean-field approximation to model the interactions, which in this case is the demagnetization field, suggests a general technique to quantify interactions in magnetic systems.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5822-5824 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetotransport properties of iron thin films grown by molecular-beam epitaxy (MBE) have been investigated. The films were grown on (110) GaAs substrates and were allowed to develop a natural oxide. The iron oxide on the free surface is FeO and has an antiferromagnetic transition temperature on the order of 200 K. This antiferromagnetic oxide provides an exchange bias for the iron film at low temperatures. Although it is usual to study exchange coupling with magnetization measurements, we have used the low-temperature magnetotransport properties of the films to study the exchange coupling and compare it to models of this phenomenon.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For many materials that can be magnetized, part of the magnetization process may be attributed to a rotation of the magnetization vector. In this context, a combination of the longitudinal and transverse magneto-optical Kerr effects are used to detect two orthogonal magnetization components in single-crystal Fe/GaAs (110) thin films. Hysteresis curves obtained by this magneto-optical technique are presented for fields along the in-plane [001], [11¯0], and [11¯1] crystal directions. For those curves that show signs of rotation, these data are simulated using a coherent rotation mechanism for the magnetization process and Fresnel reflection coefficients for the two Kerr effects. From the experimental data, it is found that the [11¯1] curves have shapes that are indicative of a rotational process. On the other hand, both the [001] and [11¯0] have magnetization curves that do not follow a simple rotation. From the coherent rotation model, there is qualitative agreement between the modeled and experimental data for the [11¯1].
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5868-5870 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of the isothermal remanent magnetization Mr and the dc demagnetization remanence Md have been made on single crystals of YBa2Cu3O7 with the applied magnetic field parallel to the c axis. Plots of Md vs Mr indicate the presence of interactions when the usual interpretation developed for ferromagnetic systems is applied. However, this interpretation neglects the intrinsic response of a superconductor to expel the flux with supercurrents. It is found that the plots, although suggesting repulsive interactions, are qualitatively explained by the Bean critical state model. In addition the use of the Md vs Mr plots in connection with the Bean model provides an alternative technique to determine critical currents.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5836-5836 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to understand the transport properties of multilayer systems, three different series of sputtered Fe/Cu multilayer films were examined by low-frequency ac resistance measurements. In each series, the total thickness of the film was maintained at approximately 2000 A(ring) while the bilayer thickness was varied from 20 to 300 A(ring). The three multilayer series differ in the ratios of Fe to Cu in a bilayer. The Fe:Cu ratios examined here are 1:3, 1:1, and 3:1. Transport and magnetotransport measurements were done on these films at temperatures of 296, 77, and 4.2 K with in-plane fields up to 10 KOe. As expected, for each Fe:Cu series the resistivities increase with decreasing bilayer thickness. Furthermore, comparing the different series, the higher Cu ratios give smaller resistivities. From the magnetotransport measurements, the anisotropic magnetoresistance also increases with decreasing bilayer thickness and appears to be linearly related to the resistivity of the multilayer, especially at the lower temperatures. For the highest Cu ratio, Fe:Cu 1:3, the AMR was unmeasureable from the thinnest periods at 296 K but becomes significant at the lower temperatures.
    Type of Medium: Electronic Resource
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