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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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In-plane and out-of-plane uniaxial anisotropies in rectangular arrays of circular dots studied by ferromagnetic resonance

G. N. Kakazei, P. E. Wigen, K. Yu. Guslienko, R. W. Chantrell, N. A. Lesnik, V. Metlushko, H. Shima, K. Fukamichi, Y. Otani, and V. Novosad

J. Appl. Phys. 93, 8418 (2003); http://dx.doi.org/10.1063/1.1556978 (3 pages) | Cited 15 times

Online Publication Date: 9 May 2003

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Ferromagnetic resonance at 9.2 GHz (X band) was used to characterize the uniaxial magnetic anisotropies in rectangular arrays of submicron circular Ni dots. The in-plane anisotropy, originated from interdot interactions in the rectangular lattice, and the perpendicular anisotropy, due to individual dot shape and magnetostriction, were explored. For in-plane dependencies of the resonance field (Hr), the main resonance mode angular dependence was well described by the standard Kittel formula. As the interdot distances decreased from 800 to 50 nm, the in-plane uniaxial anisotropy field changed from 5 to 130 Oe, in reasonable agreement with calculations. Simultaneously, the position of perpendicular Hr increased from 6.38 to 6.83 kOe, also following Kittel’s formula. © 2003 American Institute of Physics.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.30.Gw Magnetic anisotropy
75.50.Cc Other ferromagnetic metals and alloys
75.70.-i Magnetic properties of thin films, surfaces, and interfaces
75.75.-c Magnetic properties of nanostructures

Magnetoresistance study in NiFe–Al–NiFe single-electron tunneling devices

J. H. Shyu, Y. D. Yao, C. D. Chen, and S. F. Lee

J. Appl. Phys. 93, 8421 (2003); http://dx.doi.org/10.1063/1.1556979 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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Magnetoresistance in NiFe–Al–NiFe single-electron tunneling device has been studied at temperatures between 0.066 and 0.8 K and in magnetic fields up to 3 T. The competition effect among the superconducting, the Coulomb blockade, and the magnetic tunneling has been experimentally investigated. An enhancement effect of the tunneling magnetoresistance due to the superconductivity of the Al island has been observed in the nonlinear range of the current–voltage I–V characteristics. The superconducting critical magnetic fields obtained from the magnetoresistance curves are roughly decreased from 1.5±0.1 to 1.3±0.1 T, and 1.2±0.1 T for temperature increasing from 66 to 400 mK, and 800 mK, respectively. For Al island in its normal state, the resistance of the NiFe–Al–NiFe single-electron tunneling device is roughly 40 kΩ and is insensitive to the current variation. However, in general, the resistance increases with decreasing the current for the central Al island in its superconducting state. © 2003 American Institute of Physics.
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85.35.Gv Single electron devices
75.47.Np Metals and alloys
74.50.+r Tunneling phenomena; Josephson effects
73.23.Hk Coulomb blockade; single-electron tunneling

Magnetoresistance and magnetic force microscopy studies in Ni80Fe20 disk- and ring-patterned wires

J. L. Tsai, Y. D. Yao, B. S. Han, S. F. Lee, C. Yu, T. Y. Chen, E. W. Huang, and D. J. Zheng

J. Appl. Phys. 93, 8424 (2003); http://dx.doi.org/10.1063/1.1558673 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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We have investigated the magnetization reversal process of the disk-, ring-, and center dot ring-patterned Ni80Fe20 wires. For the fields applied perpendicular to the wire direction, interesting shape dependent magnetoresistance (MR) ratios were found. The MR ratios were varied from 0.8%, 0.65%, and 0.4% at room temperature and 1.7%, 1.5%, and 1.1% at 10 K for the disk-, ring-, and center dot ring-patterned wires. For the same wires, the switching field is reduced from −170, −110, and −90 Oe at room temperature to −140, −70, and −20 Oe at 10 K. These results were due to the shape anisotropy and domain-wall motion. The anisotropy MR (AMR) ratios measured at 10 K of the disk-, ring-, and center dot ring-patterned wires were 1.9±0.1%, 1.7±0.1%, and 1.3±0.1%, respectively, it is almost even the same (1.1±0.1%) at room temperature. We have observed that the center dot reduces the MR ratio and increases magnetic saturation field of the nanosize Ni80Fe20 wires. © 2003 American Institute of Physics.
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75.75.-c Magnetic properties of nanostructures
75.47.Np Metals and alloys
68.37.Rt Magnetic force microscopy (MFM)
75.60.Jk Magnetization reversal mechanisms
75.30.Gw Magnetic anisotropy
75.70.Kw Domain structure (including magnetic bubbles and vortices)

Quantum transport properties in ferromagnetic nanorings at low temperature

S. Kasai, E. Saitoh, and H. Miyajima

J. Appl. Phys. 93, 8427 (2003); http://dx.doi.org/10.1063/1.1558333 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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The low-temperature magnetoresistance in ferromagnetic Ni and Fe19Ni81 nanorings were studied. Although the aperiodic fluctuation and the periodic oscillation were observed in Fe19Ni81 nanoring, the periodic oscillation disappears in Ni nanoring. The estimated phase coherence length in Ni nanoring is about 80 nm, which is much smaller than that in Fe19Ni81 nanoring (∼500 nm). These results imply that there exists a mechanism, such as coupling between conduction electron and local magnetic anisotropy. © 2003 American Institute of Physics.
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72.15.Gd Galvanomagnetic and other magnetotransport effects
75.47.Np Metals and alloys
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.23.-b Electronic transport in mesoscopic systems
75.50.Bb Fe and its alloys
75.50.Cc Other ferromagnetic metals and alloys
61.46.-w Structure of nanoscale materials
73.63.-b Electronic transport in nanoscale materials and structures
75.50.Tt Fine-particle systems; nanocrystalline materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Dynamics of a magnetic domain wall in magnetic wires with an artificial neck

A. Himeno, T. Ono, S. Nasu, K. Shigeto, K. Mibu, and T. Shinjo

J. Appl. Phys. 93, 8430 (2003); http://dx.doi.org/10.1063/1.1556980 (3 pages) | Cited 35 times

Online Publication Date: 9 May 2003

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Magnetization reversal in submicron magnetic wires consisting of a NiFe/Cu/NiFe trilayer with an artificial neck was investigated by utilizing the giant magnetoresistance effect. A magnetic domain wall was injected into the wire by a local magnetic field applied at the end of the wire. Pinning and depinning of the magnetic domain wall were detected as sharp changes in resistance. It was found that the neck works as a pinning site of a domain wall and that the depinning field increases with a decrease of the neck width. © 2003 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
75.47.De Giant magnetoresistance
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys

Random telegraph noise in a nickel nanoconstriction

O. Céspedes, G. Jan, M. Viret, M. Bari, and J. M. D. Coey

J. Appl. Phys. 93, 8433 (2003); http://dx.doi.org/10.1063/1.1556981 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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Nickel nanoconstrictions about 20 nm wide produced by electron beam lithography in a 60 nm nickel film exhibit resistivities in the kΩ range with a nonlinear and asymmetric I–V characteristic. Noise spectra of the contacts sometimes deviate from 1/f behavior due to random telegraph fluctuations at room temperature with a frequency in the 10 Hz range. The resistance fluctuations between the two states are about 0.1%. The time spent in the high resistance state increases as we increase the temperature, and the discrete fluctuations eventually disappear with an increase of the temperature of more than about 15 °C. An explanation is proposed in terms of electron-wind electromigration which interacts with the narrow domain wall formed at the nanocontact. © 2003 American Institute of Physics.
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75.75.-c Magnetic properties of nanostructures
73.63.Rt Nanoscale contacts
73.50.Td Noise processes and phenomena
66.30.Qa Electromigration
81.07.Lk Nanocontacts
81.16.Nd Micro- and nanolithography
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Cc Other ferromagnetic metals and alloys

Magnetic-field dependence of conductance quantization in ferromagnetic point contacts

M. Shimizu, E. Saitoh, and H. Miyajima

J. Appl. Phys. 93, 8436 (2003); http://dx.doi.org/10.1063/1.1558334 (2 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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The conductance in ferromagnetic Ni point contacts has been investigated by using break junction techniques. We successfully kept each conductance plateau for about a minute. Reversible switching of the quantized conductance by the application of the magnetic field was observed. These results suggest that the mechanical aspect of quantum point contacts (QPC) formation and the local magnetic property around Ni QPC can affect the conductance quantization in Ni QPC. © 2003 American Institute of Physics.
Show PACS
73.23.-b Electronic transport in mesoscopic systems
73.63.Rt Nanoscale contacts
75.50.Cc Other ferromagnetic metals and alloys
03.65.-w Quantum mechanics
81.07.Lk Nanocontacts
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