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21 Jan 2002

Volume 80, Issue 3, pp. 341-531

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Properties of a Fe/GaAs(001) hybrid structure grown by molecular-beam epitaxy

Y. Chye, V. Huard, M. E. White, and P. M. Petroff

Appl. Phys. Lett. 80, 449 (2002); http://dx.doi.org/10.1063/1.1434302 (3 pages) | Cited 26 times

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We report on the epitaxy of Fe thin films on GaAs(001) using molecular-beam epitaxy with two different growth methods aimed at suppressing Fe and GaAs interdiffusion. These methods make use of low-temperature deposition at −150 °C and/or of an ultrathin Al interlayer, respectively. Good-quality single-crystal Fe films were obtained. The magnetic properties of the Fe films show square hysteresis loops and clear in-plane magnetic anisotropy with well-defined easy hard axes. The photoluminescence of an Al0.3Ga0.7As/GaAs quantum well in close proximity to the Fe film is measured in order to examine the quality of the Fe/GaAs interface. © 2002 American Institute of Physics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Ct Interface structure and roughness
68.35.Fx Diffusion; interface formation
68.55.A- Nucleation and growth
68.65.Fg Quantum wells
75.30.Gw Magnetic anisotropy
75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
78.67.De Quantum wells
81.05.Ea III-V semiconductors

Dependences of the activation volumes on Ar sputtering pressure in Co/Pt multilayers prepared by dc magnetron sputtering

Yoon-Chul Cho, Sug-Bong Choe, and Sung-Chul Shin

Appl. Phys. Lett. 80, 452 (2002); http://dx.doi.org/10.1063/1.1435405 (3 pages) | Cited 5 times

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We investigated the wall-motion and nucleation activation volumes of Co/Pt multilayer films prepared by dc magnetron sputtering under various Ar sputtering pressures. Delicate analysis of time-resolved domain evolution patterns reveals that the nucleation activation volume is generally smaller than the wall-motion activation volume in all the samples, which is consistent with the nucleation-dominant magnetization reversal behavior observed in this system. Interestingly, the activation volume is found to decrease with increasing Ar pressure, despite a decreasing trend in saturation magnetization. Decreasing grain size with increasing Ar pressure, smaller than the typical size of a Co single domain, is believed to be the origin of the unexpected observation. © 2002 American Institute of Physics.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.70.Kw Domain structure (including magnetic bubbles and vortices)
81.15.Cd Deposition by sputtering
68.65.Ac Multilayers
75.60.Ch Domain walls and domain structure
75.60.Jk Magnetization reversal mechanisms
81.07.-b Nanoscale materials and structures: fabrication and characterization

Interface reaction of Ta/Ni81Fe19 or Ni81Fe19/Ta and its suppression

G. H. Yu, H. C. Zhao, M. H. Li, F. W. Zhu, and W. Y. Lai

Appl. Phys. Lett. 80, 455 (2002); http://dx.doi.org/10.1063/1.1433913 (3 pages) | Cited 10 times

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Ta/Ni81Fe19 and Ni81Fe19/Ta structures are commonly used in the magnetic multilayers with giant magnetoresistance. For a Ta/Ni81Fe19/Ta fundamental structure, Ta seed and Ta cap layers resulted in a loss of moment equivalent to a magnetically dead layer of thickness 1.6±0.2 nm. In order to find out the reason, the composition and chemical states at the interface regions of Ta/Ni81Fe19 and Ni81Fe19/Ta were studied using the x-ray photoelectron spectroscopy and peak decomposition technique. The results show that there are thermodynamically favorable reactions at the Ta/Ni81Fe19 and Ni81Fe19/Ta interfaces: 2Ta+Ni = NiTa2. However, the thickness of a magnetically dead layer was significantly reduced by the insertion of a small amount of Bi in the Ta/Ni81Fe19/Ta structure. This result indicates that a surfactant Bi can suppress the interface reaction in multilayers. © 2002 American Institute of Physics.
Show PACS
68.35.Fx Diffusion; interface formation
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
79.60.Jv Interfaces; heterostructures; nanostructures
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Electronic spin detection in molecules using scanning-tunneling- microscopy-assisted electron-spin resonance

C. Durkan and M. E. Welland

Appl. Phys. Lett. 80, 458 (2002); http://dx.doi.org/10.1063/1.1434301 (3 pages) | Cited 96 times

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By combining the spatial resolution of a scanning-tunneling microscope (STM) with the electronic spin sensitivity of electron-spin resonance, we show that it is possible to detect the presence of localized spins on surfaces. The principle is that a STM is operated in a magnetic field, and the resulting component of the tunnel current at the Larmor (precession) frequency is measured. This component is nonzero whenever there is tunneling into or out of a paramagnetic entity. We have succeeded in obtaining spectra from free radical molecules from which the g factor of a spin entity may be inferred. For the molecules studied here, α,γ-bisdiphenylene-β-phenylallyl, g was found to be 2±0.1. © 2002 American Institute of Physics.
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76.30.Rn Free radicals
07.79.Cz Scanning tunneling microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Fabrication of magnetic microfiltration systems using soft lithography

Tao Deng, Mara Prentiss, and George M. Whitesides

Appl. Phys. Lett. 80, 461 (2002); http://dx.doi.org/10.1063/1.1436282 (3 pages) | Cited 54 times

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Arrays of nickel posts were used as magnetic elements in a microfiltration device that is compatible with microfluidic systems. The combination of microtransfer molding—a soft lithography technique—and electrodeposition generated nickel posts ∼7 μm in height and ∼15 μm in diameter inside a microfluidic channel. Once magnetized by a magnetic field from an external, permanent, neodymium–iron–boron magnet, these nickel posts generated strong magnetic field gradients and efficiently trapped superparamagnetic beads moving past them in a flowing stream of water. These nickel post arrays were also used to separate magnetic beads from nonmagnetic beads. © 2002 American Institute of Physics.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems
85.70.-w Magnetic devices
85.40.Hp Lithography, masks and pattern transfer
75.50.Ww Permanent magnets
81.15.Pq Electrodeposition, electroplating

Electrical transport and magnetoresistance in thick films of lanthanum calcium manganite prepared by tape casting

G. Srinivasan and E. T. Rasmussen

Appl. Phys. Lett. 80, 464 (2002); http://dx.doi.org/10.1063/1.1436283 (3 pages) | Cited 2 times

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The observation of unique thickness-dependent resistivity and magnetoresistance is reported in thick films of La0.7Ca0.3MnO3 synthesized by tape casting. Samples were prepared from tapes with layer thickness L ranging from 6 to 40 μm. Ferromagnetic resonance was used to probe the homogeneity of the films. The maximum zero-field electrical resistivity ρm(0) and low-field magnetoresistance (MR) data show: (i) an exponential drop in ρm(0) with increasing L (an inverse square dependence) and (ii) an exponential increase in MR with L (a square-root dependence). The results are in qualitative agreement with tunneling-assisted electrical transport. © 2002 American Institute of Physics.
Show PACS
75.47.Gk Colossal magnetoresistance
73.40.Gk Tunneling
75.50.Dd Nonmetallic ferromagnetic materials
75.47.De Giant magnetoresistance
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
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