APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

1 Mar 1999

Volume 74, Issue 9, pp. 1191-1347

Return to All Sections
back to top
RSS Feeds

High-Tc directly coupled direct current SQUID gradiometer with flip-chip flux transformer

Y. J. Tian, S. Linzen, F. Schmidl, L. Dörrer, R. Weidl, and P. Seidel

Appl. Phys. Lett. 74, 1302 (1999); http://dx.doi.org/10.1063/1.123531 (3 pages) | Cited 17 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have designed and fabricated a flip-chip-type gradiometer as a sensor for measurement of weak magnetic signals. The gradiometer consists of a directly coupled direct current superconducting quantum interference device (SQUID) gradiometer coupled to a flux transformer made from a YBa2Cu3O7∗/YBa2Cu3O7/CeO2/YSZ multilayer on 2 in. Si wafer, where YBa2Cu3O7∗(YBCO∗) is a nonsuperconducting crystalline film. The coupling coefficient of 0.18 is obtained for the flip-chip gradiometer. The transformer increases effectively the resolutions of the gradiometer. We obtain a magnetic field gradient resolution of 73 fT cm−1 Hz−1/2 in the white region, and 596 fT cm−1 Hz−1/2 at 1 Hz. The magnetocardiograms were successfully measured at a distance of nearly 100 mm from the gradiometer center to the human heart in a shielded room. © 1999 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
85.25.Dq Superconducting quantum interference devices (SQUIDs)
07.55.Ge Magnetometers for magnetic field measurements

Exchange biasing in ferromagnetic amorphous wires: A controllable micromagnetic configuration

J. J. Freijo, A. Hernando, M. Vázquez, A. Méndez, and V. R. Ramanan

Appl. Phys. Lett. 74, 1305 (1999); http://dx.doi.org/10.1063/1.123532 (3 pages) | Cited 5 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Nonmagnetostrictive Co-rich amorphous wires, 130 μm in diameter, were stress annealed to induce a transverse anisotropy. The resultant structure consists of a circular-magnetization single domain except in a thin core, 2 μm in diameter, where magnetization is axially oriented. The wall interconnecting the outer shell with the core magnetization induces a local helical anisotropy during the annealing. As a consequence, a strong link between the magnetization directions in both regions appears. It is shown that direct current axial fields produce remarkable shifts of the circular hysteresis loops. © 1999 American Institute of Physics.
Show PACS
75.50.Cc Other ferromagnetic metals and alloys
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy

Measuring the gigahertz response of recording heads with the magnetic force microscope

Roger Proksch, Peter Neilson, Shane Austvold, and J. J. Schmidt

Appl. Phys. Lett. 74, 1308 (1999); http://dx.doi.org/10.1063/1.123533 (3 pages) | Cited 23 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We compare two different techniques for measuring the high frequency response of recording heads using a magnetic force microscope. The first technique is based on driving the recording head with a high frequency current. We separated the high and low frequency response of the recording head by making two measurements, one with the current on, one with the current off. The second technique is based on amplitude modulation of the high frequency current driving the recording head. This technique has the advantage of separating the low and high frequency response in a single measurement. We used both of these techniques to study the spatially dependent response of recording heads operating up to and beyond 1 GHz. © 1999 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Magnetic phase diagram of ultrathin Co/Si(111) film studied by surface magneto-optic Kerr effect

Jyh-Shen Tsay and Yeong-Der Yao

Appl. Phys. Lett. 74, 1311 (1999); http://dx.doi.org/10.1063/1.123534 (3 pages) | Cited 28 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A magnetic phase diagram of the ultrathin Co/Si(111) film deposited at 300 K has been established by the surface magneto-optic Kerr effect technique. The temperature, where ferromagnetism vanishes, increases from 375 to 625 K as the coverage of the Co film increases from 3.5 to 16 monolayers. A quantitative calculation of the normalized Auger signal of CoSi2 shows that the calculated values lie between the experimental measured Auger signals before and after ferromagnetism vanishes for films with coverage between 3.5 and 9.1 monolayers. For samples with higher coverage, the experimental data are smaller than that by calculation. This may be qualitatively explained by Co atoms escaping from the CoSi2 phase to diffuse into the Si substrate. The disappearance of ferromagnetism is mainly attributed to silicide formation. © 1999 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Cc Other ferromagnetic metals and alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
78.20.Ls Magneto-optical effects
75.70.Rf Surface magnetism
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.35.Fx Diffusion; interface formation
78.66.Bz Metals and metallic alloys

Increasing the exchange-bias field of Ni0.5Co0.5O films by microstructural control

Dinesh Martien, Kentaro Takano, A. E. Berkowitz, and David J. Smith

Appl. Phys. Lett. 74, 1314 (1999); http://dx.doi.org/10.1063/1.123535 (3 pages) | Cited 10 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The exchange-bias field produced by antiferromagnetic monoxide films has been shown to scale with the density of uncompensated interfacial spins. The uncompensated spin density is inversely proportional to the interfacial grain diameter. Accordingly, we have prepared Ni0.5Co0.5O films in which the average interfacial grain diameter is small, but the grains are elongated, thus avoiding thermally activated fluctuations of the spin system associated with small grain volumes. The exchange-bias field remained inversely proportional to the interfacial grain diameter, and was increased to twice its previous maximum value without introducing significant thermal instability. © 1999 American Institute of Physics.
Show PACS
75.50.Ee Antiferromagnetics
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Et Exchange and superexchange interactions
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Observation of supercurrent distribution in YBa2Cu3O7−δ thin films using THz radiation excited with femtosecond laser pulses

S. Shikii, T. Kondo, M. Yamashita, M. Tonouchi, M. Hangyo, M. Tani, and K. Sakai

Appl. Phys. Lett. 74, 1317 (1999); http://dx.doi.org/10.1063/1.123536 (3 pages) | Cited 17 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have demonstrated that the supercurrent distribution in current-biased YBa2Cu3O7−δ thin films can be obtained by measuring the radiation power of THz electromagnetic pulses excited with femtosecond laser pulses. As the radiation power is proportional to the square of the bias current density at the laser spot position, the two-dimensional current distribution can be obtained from the intensity distribution of THz radiation by scanning the laser spot. The characteristic supercurrent distribution is analyzed by using the critical-state model. © 1999 American Institute of Physics.
Show PACS
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
74.25.Sv Critical currents
74.25.N- Response to electromagnetic fields

Contributions of individual Fe sites to magnetocrystalline anisotropy of Y2Fe17−xGax compounds

Zhao-hua Cheng, Bao-gen Shen, Fang-wei Wang, and H. Kronmüller

Appl. Phys. Lett. 74, 1320 (1999); http://dx.doi.org/10.1063/1.123537 (3 pages) | Cited 4 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
At present, individual Fe sites anisotropies of Y2Fe17 compound cannot be directly measured by ordinary magnetization measurement. Alternatively, they are derived from the relationship between occupancy factors of Fe atoms at different sites and anisotropy constants of Y2Fe17−xGax compounds. It is found that only Fe atoms at 9d site have a significantly positive contribution to the uniaxial anisotropy, while those at 6c and 18h sites have strongly negative contributions; the contribution of Fe atoms at 18f site is slightly negative and less important. The planar anisotropy is rapidly weakened and finally a uniaxial anisotropy is induced by the Ga substitution. These results can be explained by the preferential occupancies of Ga atoms at 18h site for low Ga concentration as well as 6c and 18f sites for high Ga concentration. © 1999 American Institute of Physics.
Show PACS
75.50.Bb Fe and its alloys
61.66.Dk Alloys

Superconducting transport properties of 2.2-GeV Au-ion irradiated c-axis twist Bi2Sr2CaCu2O8+δ bicrystals

Qiang Li, Y. N. Tsay, M. Suenaga, G. Wirth, G. D. Gu, and N. Koshizuka

Appl. Phys. Lett. 74, 1323 (1999); http://dx.doi.org/10.1063/1.123538 (3 pages) | Cited 6 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
2.2-GeV Au-ions irradiation is used to study the effect of columnar defects on the transport properties of Bi2Sr2CaCu2O8+δ (Bi2212) bicrystals with high quality c-axis twist grain boundary. The studies show a similar increase in the irreversible temperature determined within the single crystals and across the grain boundaries after irradiation. However, the irradiation enhancement on the grain boundary critical current (Ic) at low temperatures is small, compared to the more than an order of magnitude increase of single crystal Ic. © 1999 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
61.82.Ms Insulators
74.25.Sv Critical currents
61.72.Mm Grain and twin boundaries
61.80.Jh Ion radiation effects
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close