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

8 Oct 2001

Volume 79, Issue 15, pp. 2309-2491

Return to All Sections
back to top
RSS Feeds

Enhancement of magnetic coercivity and ferromagnetic transition temperature by proximity effects in the GaMnAs–ZnMnSe multilayer system

X. Liu, Y. Sasaki, and J. K. Furdyna

Appl. Phys. Lett. 79, 2414 (2001); http://dx.doi.org/10.1063/1.1409587 (3 pages) | Cited 19 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated the degree to which the ferromagnetic properties of GaMnAs can be modified by the proximity of a Mn-based magnetic layer in which the Mn–Mn interactions are aniferromagnetic. Epitaxial GaMnAs capped with ZnMnSe was used for this purpose. We observed that the presence of the ZnMnSe overlayer leads to a dramatic modification of the coercive field of GaMnAs, which remains high almost up to the Curie temperature. The presence of ZnMnSe overlayers also leads to a significant increase in the Curie temperature of GaMnAs, as compared to “bare” GaMnAs. © 2001 American Institute of Physics.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Pp Magnetic semiconductors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.30.Et Exchange and superexchange interactions
75.50.Dd Nonmetallic ferromagnetic materials

Microwave-power handling capability of HgBa2CaCu2O6+δ superconducting microstrip lines

Roberto S. Aga, Yi-Yuan Xie, Shao-Lin Yan, Judy Z. Wu, and Siyuan S. Han

Appl. Phys. Lett. 79, 2417 (2001); http://dx.doi.org/10.1063/1.1409950 (3 pages) | Cited 12 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Measurement of microwave-power handling capability, performed on high-temperature superconducting HgBa2CaCu2O6+δ (Hg-1212) microstrip lines, was carried out at a microwave frequency of 1 GHz and temperatures ranging from 77 to 120 K. These samples were prepared using a different route in which direct patterning on Hg-1212 was avoided to minimize their moisture exposure. Microwave input power was swept to high levels to drive the samples from a linear (less dissipative) state into nonlinear (more dissipative) state. Critical input power (Pc) was determined to be the crossover between the two states. The Pc values observed for Hg-1212 microstrip lines were 29.3, 25.8, 23, and 16 dBm at 80, 90, 100, and 110 K, respectively. These Pc values, comparable with the best obtained so far on other superconductors at lower temperatures, are orders of magnitude better at 100 K or higher, suggesting that Hg-1212 is promising for microwave devices and circuits operating above 100 K or higher temperatures. © 2001 American Institute of Physics.
Show PACS
84.40.Az Waveguides, transmission lines, striplines
85.25.-j Superconducting devices
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures

Superconducting quantum interference device based on MgB2 nanobridges

Alexander Brinkman, Dick Veldhuis, Dragana Mijatovic, Guus Rijnders, Dave H. A. Blank, Hans Hilgenkamp, and Horst Rogalla

Appl. Phys. Lett. 79, 2420 (2001); http://dx.doi.org/10.1063/1.1407864 (3 pages) | Cited 53 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The superconductor MgB2, with a transition temperature of 39 K, has significant potential for future electronics. An essential step is the achievement of Josephson circuits, of which the superconducting quantum interference device (SQUID) is the most important. Here, we report Josephson quantum interference in superconducting MgB2 thin films. Modulation voltages of up to 30 μV are observed in an all-MgB2 SQUID, based on focused-ion-beam patterned nanobridges. These bridges, with a length scale <100 nm, have outstanding critical current densities of 7×106 A/cm2 at 4.2 K. © 2001 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.50.+r Tunneling phenomena; Josephson effects
85.25.Cp Josephson devices
74.78.-w Superconducting films and low-dimensional structures

Noise reduction mechanisms in laminated antiferromagnetically coupled recording media

S. N. Piramanayagam, J. P. Wang, C. H. Hee, S. I. Pang, T. C. Chong, Z. S. Shan, and L. Huang

Appl. Phys. Lett. 79, 2423 (2001); http://dx.doi.org/10.1063/1.1407855 (3 pages) | Cited 9 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Experimental methods to obtain remnant moment-thickness product (Mrδ) reduction in the laminated antiferromagnetically coupled (LAC) recording media is described. The results indicate that the reduction in Mrδ (or, indirectly, a reduction in noise) can be obtained by altering the antiferromagnetic coupling constant J, or by the parameters of the underlayer such as anisotropy constant (Ku2), thickness (t2), etc. A method to enhance J by intrinsic means is proposed by which a high exchange field of about 1900 Oe can be obtained. Thermal energy has been found to help in obtaining a Mrδ reduction in LAC media. Substrates with lower surface roughness also enhance the Mrδ reduction. © 2001 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.35.Ct Interface structure and roughness
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Crystallographic texture and magnetic anisotropy of α-Fe/Nd2Fe14B nanocomposites prepared by controlled melt spinning

X. Y. Zhang, Y. Guan, L. Yang, and J. W. Zhang

Appl. Phys. Lett. 79, 2426 (2001); http://dx.doi.org/10.1063/1.1409269 (3 pages) | Cited 20 times

Full Text: Read Online (HTML) | Download PDF


See Also: Erratum

Show Abstract
In this study, α-Fe/Nd2Fe14B nanocomposite magnets with strong crystallographic texture were prepared by controlled melt spinning. For a relatively low wheel speed of 10 m/s, the c-axis texture of the Nd2Fe14B crystals is predominantly perpendicular to the plane of the ribbon, but it switches to parallel to the ribbon plane direction at a higher wheel speed of 20 m/s. The magnets show strong magnetic anisotropy between in and out of the ribbon planes. High remanence of 0.74Ms and a large energy product of 24.3 MGOe were observed parallel to the ribbon plane direction in the magnets prepared at a wheel speed of 20 m/s. © 2001 American Institute of Physics.
Show PACS
75.50.Ww Permanent magnets
75.50.Bb Fe and its alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.07.Bc Nanocrystalline materials
81.05.Bx Metals, semimetals, and alloys

High critical current densities in superconducting MgB2 thin films

S. H. Moon, J. H. Yun, H. N. Lee, J. I. Kye, H. G. Kim, W. Chung, and B. Oh

Appl. Phys. Lett. 79, 2429 (2001); http://dx.doi.org/10.1063/1.1407854 (3 pages) | Cited 62 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Superconducting MgB2 thin films were prepared on Al2O3(0001) and MgO(100) substrates. Boron thin films were deposited by the electron-beam evaporation followed by postannealing process with magnesium. Proper postannealing conditions were investigated to grow good superconducting MgB2 thin films. The x-ray diffraction patterns showed randomly oriented growth of MgB2 phase in our thin films. The surface morphology was examined by scanning electron microscope and atomic force microscope. Critical current density (JC) measured by transport method was about 107 A/cm2 at 15 K, and superconducting transition temperature (TC) was ∼39 K in the MgB2 thin films on Al2O3. © 2001 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents
74.10.+v Occurrence, potential candidates

Paramagnetism and antiferromagnetic d–d coupling in GaMnN magnetic semiconductor

M. Zając, J. Gosk, M. Kamińska, A. Twardowski, T. Szyszko, and S. Podsiadło

Appl. Phys. Lett. 79, 2432 (2001); http://dx.doi.org/10.1063/1.1406558 (3 pages) | Cited 77 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The magnetization of Ga1−xMnxN (x<0.1) crystals was measured as a function of the magnetic field and temperature. Paramagnetic behavior typical of spin S = 5/2 expected for Mn2+ (d5) magnetic centers was observed in the temperature range of 2 K<T<300 K. On the other hand, antiferromagnetic coupling between Mn ions was clearly visible. The nearest neighbor (NN) coupling constant JNN/kB = −1.9 K was estimated from the temperature dependence of the magnetization. © 2001 American Institute of Physics.
Show PACS
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.05.Ea III-V semiconductors
75.50.Pp Magnetic semiconductors
75.20.Ck Nonmetals
75.50.Ee Antiferromagnetics
75.30.Et Exchange and superexchange interactions

High transport critical current density obtained for powder-in-tube-processed MgB2 tapes and wires using stainless steel and Cu–Ni tubes

H. Kumakura, A. Matsumoto, H. Fujii, and K. Togano

Appl. Phys. Lett. 79, 2435 (2001); http://dx.doi.org/10.1063/1.1407856 (3 pages) | Cited 121 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
MgB2 tapes and wires were fabricated by the powder-in-tube method. Stainless steel and Cu–Ni tubes were used as sheath materials, and no heat treatment was applied. The tapes made of stainless steel showed transport critical current density Jc of about 10 000 A/cm2 at 4.2 K and 5 T. A high Jc of about 300 000 A/cm2 was obtained by extrapolating the Jc–B curves to zero field. Multifilamentary (seven-core) MgB2 wire was successfully fabricated using Cu–Ni tubes. For both tapes and wires, the grain connectivity of MgB2 was as good as a high-pressure sintered bulk sample. However, the Jc of the Cu–Ni sheathed wire was lower than the stainless steel sheathed tape due to the lower packing density of MgB2. © 2001 American Institute of Physics.
Show PACS
74.72.-h Cuprate superconductors
84.71.Mn Superconducting wires, fibers, and tapes
74.25.Sv Critical currents

Low-frequency noise in high-transition-temperature superconducting multilayer magnetometers in ambient magnetic fields

Hsiao-Mei Cho, Y. T. Andresen, John Clarke, M. S. DiIorio, K.-Y. Yang, and S. Yoshizumi

Appl. Phys. Lett. 79, 2438 (2001); http://dx.doi.org/10.1063/1.1410344 (3 pages) | Cited 6 times

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Each magnetometer consisted of a dc superconducting quantum interference device (SQUID), with the YBa2Cu3O7−x washer patterned into 4 μm lines, coupled to a multiturn, multilayer flux transformer containing flux dams. The noise at 1 Hz did not increase when bare SQUIDs or magnetometers were cooled and operated in fields up to values well above the magnetic field of the earth. When the magnetic field was changed, the noise in a bare SQUID was constant up to a threshold field of 12 μT. The addition of a flux transformer containing flux dams increased the magnetic field sensitivity by a factor of 43, while reducing the threshold field only moderately, to 5 μT. © 2001 American Institute of Physics.
Show PACS
07.55.Ge Magnetometers for magnetic field measurements
85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.78.-w Superconducting films and low-dimensional structures
74.78.Fk Multilayers, superlattices, heterostructures
74.72.-h Cuprate superconductors
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close