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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Investigation of the crystallographic texture and interface roughness on CoCrPt /Ti magnetic thin films

C. J. Sun, G. M. Chow, J. P. Wang, E. W. Soo, and J. H. Je

J. Appl. Phys. 93, 8725 (2003); http://dx.doi.org/10.1063/1.1540133 (3 pages) | Cited 5 times

Online Publication Date: 9 May 2003

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The structure and interface of Co74Cr16Pt10 (40 nm thick)/Ti (10 nm thick) films for perpendicular magnetic recording were studied using x-ray scattering and transmission electron microscopy. Improved out-of-plane coercivity and squareness resulted from the combined effects of higher crystallinity and better texture of the CoCrPt (002) film, and increased interface roughness. The relationship of sputtering pressure to the structural effects is discussed. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Ss Magnetic recording materials
68.55.-a Thin film structure and morphology
68.35.Ct Interface structure and roughness
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.70.Ck X-ray scattering
81.15.Cd Deposition by sputtering

Effects of Ag buffer layer on the magnetic properties of ultrathin Co/Ge(111) films

J. S. Tsay, H. Y. Nieh, C. S. Yang, Y. D. Yao, and T. S. Chin

J. Appl. Phys. 93, 8728 (2003); http://dx.doi.org/10.1063/1.1540134 (3 pages) | Cited 6 times

Online Publication Date: 9 May 2003

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The influences of an Ag buffer layer on the magnetic properties of ultrathin Co/Ge(111) films grown at ambient temperature were studied using the surface magneto-optic Kerr effect technique. Due to the intermixing of Co adatoms and Ge(111) substrate, a nonferromagnetic layer forms at the initial stage of the deposition for Co/Ge(111) films. We demonstrate experimentally that the ferromagnetic inactive layer can be reduced by introducing an Ag buffer layer and the orientation of the easy axis of magnetization remains unchanged. Three magnetic phases have been resolved for Co/Ag/Ge(111) films with a Ag thickness less than 6 monolayers. In the phase diagram, the boundary between ferromagnetic and nonmagnetic regions shifts to a lower Co thickness from 10 to 5 monolayers as the thickness of the Ag layer increases from 0 to 6 monolayers. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
78.20.Ls Magneto-optical effects

Thin Al, Au, Cu, Ni, Fe, and Ta films as oxidation barriers for Co in air

L. Gan, R. D. Gomez, C. J. Powell, R. D. McMichael, P. J. Chen, and W. F. Egelhoff

J. Appl. Phys. 93, 8731 (2003); http://dx.doi.org/10.1063/1.1543873 (3 pages) | Cited 13 times

Online Publication Date: 9 May 2003

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We have investigated the effectiveness of Al, Au, Cu, Ni, Fe, and Ta films with thicknesses up to 4 nm for protecting a Co surface from oxidation in air at room temperature. The distinct change in the Co 2p3/2 core-level line shape observed by x-ray photoelectron spectroscopy upon the oxidation of Co makes it a simple matter to identify the fractions of the Co that are in the metallic state and in the oxidized state. We find that the best choices for protecting Co from oxidation are Al and Ta. We found that Au, which is one of the most popular choices, is not particularly effective for protecting Co. © 2003 American Institute of Physics.
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81.65.Mq Oxidation
79.60.Dp Adsorbed layers and thin films

Influence of submonolayers of sodium on the spin polarization of iron outmost surfaces

Yasushi Yamauchi, Mitsunori Kurahashi, Taku Suzuki, and Xin Ju

J. Appl. Phys. 93, 8734 (2003); http://dx.doi.org/10.1063/1.1555984 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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Spin-polarized metastable deexcitation spectroscopy (SPMDS) is employed to study the electron spin polarization of Na (0.1–0.6 monolayer)/Fe(100) outermost surfaces. At the Fermi level, positive asymmetries of SPMDS spectra, which correspond to negative spin polarizations and are the same as those of the clean Fe(100) surface, are observed. The origin of this positive spin polarization and the drastic decrease in the magnitude of asymmetries of SPMDS spectra are discussed on the basis of the spin density distributions obtained by calculating the electronic structures of Na(c2×2)/Fe(100), which strongly depend on the adsorption sites, using WIEN97, a full-potential linearized augmented plane-wave method. © 2003 American Institute of Physics.
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72.25.Mk Spin transport through interfaces
75.70.Rf Surface magnetism
75.50.Bb Fe and its alloys
73.20.At Surface states, band structure, electron density of states
75.47.Np Metals and alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Surface, interface and bulk studies of NiFe nanometer films for magnetoresistive heads

M. P. Hollingworth, M. R. J. Gibbs, and E. W. Hill

J. Appl. Phys. 93, 8737 (2003); http://dx.doi.org/10.1063/1.1543874 (3 pages) | Cited 13 times

Online Publication Date: 9 May 2003

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Polycrystalline Ni81Fe19 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. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Ss Magnetic recording materials
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Gw Magnetic anisotropy
75.70.Rf Surface magnetism
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.-c Magnetic properties of nanostructures
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Growth and magnetic properties of epitaxial ultrathin Ni films on Cu(111) using Sb as a surfactant

F. Matthes, A. Rzhevskii, L.-N. Tong, D. Venus, and C. M. Schneider

J. Appl. Phys. 93, 8740 (2003); http://dx.doi.org/10.1063/1.1540135 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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We studied the growth and magnetism of ultrathin Ni films on the (111) surface of Cu using Sb as a surfactant. For this purpose we deposited Sb under UHV conditions at room temperature onto the Cu surface prior to the Ni film growth. When the Sb precoverage exceeded a certain threshold [0.7 monolayers (ML)], pronounced intensity oscillations of the medium energy electron diffraction signal indicated a layer-by-layer growth of the deposited Ni films. Low energy electron diffraction patterns of the Ni films revealed a hexagonal structure with a threefold symmetry. Using this approach we prepared high quality epitaxial Ni(111) films up to a thickness of 20 ML and performed in situ magneto-optical Kerr measurements. At a thickness of 7–8 ML an inverse spin reorientation transition occurs from an in-plane magnetization at lower thicknesses to an out-of-plane orientation for higher thicknesses. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
68.55.A- Nucleation and growth
82.70.Uv Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions)
78.20.Ls Magneto-optical effects

Exchange bias in Co/Fe/FexMn1−x/Cu(100) ultrathin films

C. C. Kuo, W. Pan, Y. C. Chen, and Minn-Tsong Lin

J. Appl. Phys. 93, 8743 (2003); http://dx.doi.org/10.1063/1.1540136 (3 pages) | Cited 6 times

Online Publication Date: 9 May 2003

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Stable and well-grown face-centered-cubic Fe films were prepared on buffer layers with varying lattice constants by depositing FexMn1−x alloy film on Cu(100) single crystal. No ferromagnetic ordering was observed at the stage of 30 ML Fe on the FexMn1−x/Cu(100) systems in the temperature range from 100 to 350 K. Furthermore, capping of Co on Fe/FexMn1−x/Cu(100) was employed as the probe of antiferromagnetic ordering by study of exchange bias coupling in these films. The exchange bias of the hysteresis loops can be observed after field cooling of the films. Further analyses by varying the measurement temperature and Fe coverage of the films were also carried out to clarify the origin of the exchange bias coupling observed. The exchange bias field found here is attributed to the interlayer coupling between the Co and Fe–Mn films through the spacing layer Fe. © 2003 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ee Antiferromagnetics
78.20.Ls Magneto-optical effects

Antidot density-dependent reversal dynamics in ultrathin epitaxial Fe/GaAs(001)

T. A. Moore, G. Wastlbauer, J. A. C. Bland, E. Cambril, M. Natali, D. Decanini, and Y. Chen

J. Appl. Phys. 93, 8746 (2003); http://dx.doi.org/10.1063/1.1540137 (3 pages) | Cited 7 times

Online Publication Date: 9 May 2003

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Easy axis dynamic magneto-optic Kerr effect loops have been obtained from ultrathin (20 Å) epitaxial Fe/GaAs(001) patterned with antidot arrays of different densities (antidot spacings s=10 and 50 μm). The external field was driven sinusoidally in time with frequency in the range 0.01 Hz–2.3 kHz. In the low-frequency regime (f<20 Hz) coercivity Hc increases with 1/s, in agreement with existing phenomenological laws of geometric coercivity scaling in quasistatic fields, e.g., Hc=ζt/x, where t is the film thickness, x is a length parameter of the magnetic structure, and ζ is a constant of proportionality. However, in the transitional region between the low- and high-frequency regimes (20 Hz<f<1000 Hz), we find that scaling parameter ζ is no longer constant and increases with frequency: at low antidot density (s=50 μm) the coercivity in the transitional region falls to a minimum, while at high antidot density (s=10μm) it remains almost a constant. The dip in coercivity for s=50 μm is attributed to a resonance of the sweeping applied field with the domain-wall propagation in the film. Meanwhile, the suppression of the dip for s=10 μm is ascribed to a change in the relative importance of wall propagation and domain nucleation mechanisms in dynamic magnetization reversal. © 2003 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Jk Magnetization reversal mechanisms
75.50.Bb Fe and its alloys
78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.60.Ch Domain walls and domain structure
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