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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5864-5866 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we present an experimental study of the impact of the write current wave form on high frequency magnetic recording. It has been found that, at high recording frequencies, current overshoot reduces transition broadening, overwrite degradation, and nonlinear transition distortion. Results show that, to achieve fast flux reversal time, increasing write current overshoot is more effective and efficient than increasing write current amplitude. While overdriving the write head may bring the head into deep saturation, and introduces additional nonlinear transition shift, current overshoot significantly eliminates this nonlinear transition distortion by achieving fast head field rise time yet preventing the write head from deep saturation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: NiO/Ni81Fe19 bilayers with high exchange coupling, Hex, and low coercivity, Hc, were fabricated. These bilayers with NiO crystalline textures of (111), (200), and (220), and different surface/interface roughness were deposited onto a Si(100) wafer by changing the rf reactive sputtering conditions. A new parameter of exchange coupling to coercivity ratio, Hex/Hc, was used to quantify the effectiveness of the exchange bias for the bilayer film. An Hex=39 Oe and Hc=4.1 Oe were obtained from a NiO (45 nm)/NiFe (10 nm) bilayer, yielding a ratio of Hex/Hc=9.51, which was significantly higher than any previously reported results. An atomic force microscopy study showed that the key to the low coercivity was the reduction of surface roughness of the NiO/NiFe bilayer. It is proposed that the roughness-induced magnetostatic coupling in the NiFe film could be one of the main mechanisms for the relating high coercivity in NiO exchange-biased NiFe bilayer. NiO/NiFe/Co/Cu/Co/NiFe spin-valve films were deposited and a giant magnetoresistance of 6.62% and a field sensitivity of 0.83%/Oe were obtained at room temperature. ©1997 American Institute of Physics
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, a micromagnetic study of magnetic switching properties on submicron scale single layer and multilayer thin film elements is presented. Even at deep submicron scale, there exist various edge domain configurations at the saturation remanent state. It is found that the switching field of these patterned film elements can strongly depend on these edge domain configurations. If the edge domains are not controlled, switching field of a patterned magnetic film element can vary significantly during repeated switching processes. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Micromagnetic modeling and time-domain experimental measurements are combined to study spatial noise correlations between two closely recorded transitions in oriented longitudinal thin-film media. The Karhunen–Loeve expansion method is utilized to characterize the noise correlations. The analysis shows that the noise correlation of the dipulses exhibits three principle modes: amplitude variation, shift in unison, and breathing. The supralinear increase of noise at small bit intervals in well-oriented longitudinal film media is dominated by the amplitude variation, which arises from large variation of the degree of percolation between adjacent transition boundaries. The results from the micromagnetic modeling shows excellent agreement with the results obtained from the experimental time-domain noise measurements.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied keepered high coercivity CoCrTa/Cr thin film media with a Cr isolation layer between the CoCrTa storage and an overcoating of an isotropic NiFe soft magnetic layer. The influence of the thickness of the NiFe and Cr layers, and the effects of head bias current on the signal output and noise, were studied using a thin film head. The reproduced signal increased by 7.3 dB, but the signal-to-noise ratio decreased by 4 dB at a linear density of 2100 fr/mm (53.3 kfr/in.) with a 1000 A(ring) thick NiFe keeper layer. The medium noise increased with increasing NiFe thickness and the signal output decreased with decreasing Cr thickness. A low output signal obtained with very thin Cr may be due to magnetic interactions between the keeper layer and magnetic media layer. It is observed that signal distortion and timing asymmetry of the output signals depend on the thickness of the keeper layer and the head bias current. The signal distortion increased and the timing asymmetry decreased as the head bias current was increased. These results may be associated with different permeability of the keeper under the poles of the thin film head due to the superposition of head bias and bit fields.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Orthogonal narrow track magnetoresistive heads using giant magnetoresistive multilayers have been studied by micromagnetic modeling. The modeling shows that the hysteresis arises from irreversible switching of the edge-curling wall (ECW) on the side edges of the giant magnetoresistive (GMR) sensor layers. Effects of thickness and interlayer exchange coupling on the switching of the ECW are analyzed. It is also found that if the interlayer exchange coupling is ferromagnetic, the GMR orthogonal head has significant high signal amplitude.
    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 66 (1989), S. 1291-1307 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Computer simulation has been utilized to study magnetization reversal processes in CoCr perpendicular films. The model is based on the columnar structure of the film. Each column is considered to be a single crystal with perpendicular uniaxial crystalline anisotropy. The model assumes that each column is always uniformly magnetized even during its magnetization reversal. The gyromagnetic equation of motion with phenomenological Landau–Lifshitz damping is utilized to describe the magnetization rotation of this coupled system. The study focuses on the collective magnetization reversal modes of the particles due to magnetostatic interactions and intergranular exchange coupling. Low nucleation fields occur which are characterized by a planar chain nucleation mode. This yields coercivities equal to or less than the crystalline anisotropy field 2K/M. It is argued that, due to this collective process, the uniform rotation reversal mechanism for the individual particles in the film is energetically more favorable than nonuniform reversal, such as curling. Intercolumn exchange coupling significantly reduces the coercivity and an increase of the exchange coupling strength changes the magnetization behavior from "particulate'' to "continuous.''
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7061-7063 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, a systematic micromagnetic analysis of the pseudospin valve magnetic random access memory device is presented. The article focuses on the correlation between switching field variation and geometric structure of the memory elements. For an elongated memory element with flat ends, magnetization reversal always initiates from the ends, yielding nonrepeatable switching processes and fluctuating switching fields. Tapering the element ends forces the reversal to start from the center region of the element and triggers robust repeatable magnetization rotation. However, sharp tips of the tapered ends are required, which may present limitations on fabrication in practice. © 2000 American Institute of Physics.
    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 87 (2000), S. 5416-5418 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article presents a micromagnetic study of the dynamic magnetic switching process in the pole tip region of stitched-pole thin film write heads. The impacts of track width reduction and pole material saturation moment on the high frequency performance of the heads have been investigated. It is found that the magnetic switching process of the pole tip region at low recording frequencies can be characterized by three stages: the nucleation of a vortex (or vortices), followed by the motion of the vortex (or vortices), and finally the annihilation of the vortex (or vortices). At high frequencies, however, a residual vortex (or vortices) will always remain in the pole tips, resulting in lower head field amplitude. Frequency roll-off characteristics of the head field response have been calculated. The roll off is the result of residual vortex (or vortices), and the vortex moving speed limits the operational frequency range of the head. Reducing the track width lowers the head field 3 dB roll-off frequency. The simulation also finds that the use of 45/55 NiFe, which has significantly higher moment than permalloy, results in higher roll-off frequency as compared to permalloy. © 2000 American Institute of Physics.
    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 85 (1999), S. 4776-4778 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of crystalline orientation and grain size on the switching behavior for patterned face-centered-cubic Co film elements has been investigated through micromagnetic modeling. It is found that the switching field of the Co film element exhibits significant dependence on crystalline orientation and grain size. Large grain results in large switching field for polycrystalline Co film element. The switching fields of (001) and (110) oriented single crystal elements are much higher than that of the (111) oriented single crystal elements. It is also found that the effect of crystalline anisotropy on the switching behaviors strongly depends on the magnetization reversal mode. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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