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

29 Jan 2007

Volume 90, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 90, 052503 (2007); http://dx.doi.org/10.1063/1.2436715 (3 pages)

Biqin Huang, Igor Altfeder, and Ian Appelbaum
Enlarge Image | Read More
Return to All Sections
back to top
RSS Feeds

Entropy change upon magnetic field and pressure variations

N. A. de Oliveira

Appl. Phys. Lett. 90, 052501 (2007); http://dx.doi.org/10.1063/1.2434154 (3 pages) | Cited 15 times

Online Publication Date: 29 January 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this letter it is theoretically discussed the magnetocaloric effect under applied pressure and the barocaloric effect under applied magnetic field in compounds undergoing a first order magnetic phase transition. The theoretical findings of this letter point out that the magnetocaloric effect upon simultaneous variation of the magnetic field and pressure as well as the barocaloric effect in first order phase transition compounds can be very important for magnetic refrigeration technology.
Show PACS
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.10.Dg Crystal-field theory and spin Hamiltonians
65.40.G- Other thermodynamical quantities

Enhanced exchange bias coupling in Fe/FexMn1−x bilayer by reducing vertical lattice constants

Wen-Chin Lin, Bo-Yao Wang, Te-Yu Chen, Ling-Chih Lin, Yu-Wen Liao, Wei Pan, Nai-Yeou Jih, Ker-Jar Song, and Minn-Tsong Lin

Appl. Phys. Lett. 90, 052502 (2007); http://dx.doi.org/10.1063/1.2435514 (3 pages) | Cited 3 times

Online Publication Date: 29 January 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The modification of crystalline structure by epitaxial growth on different single crystals induces crucial effects on the exchange bias coupling. Due to the larger lattice constant (a0) of Cu3Au(100) (a0 = 3.75 Å), the vertical lattice constants of Fe/FexMn1−x films on Cu3Au(100) are much smaller than those of the Fe/FexMn1−x/Cu(100) system (Cu: a0 = 3.61 Å). By reducing the vertical lattice constants, the interface exchange bias coupling energy of Fe/FexMn1−x/Cu3Au(100) is enhanced to be 0.12–0.18 erg/cm2, which is approximately four times that of the Cu(100) system.
Show PACS
75.30.Et Exchange and superexchange interactions
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Bb Fe and its alloys
75.70.Ak Magnetic properties of monolayers and thin films
78.20.Ls Magneto-optical effects
68.55.-a Thin film structure and morphology

Spin-valve phototransistor

Biqin Huang, Igor Altfeder, and Ian Appelbaum

Appl. Phys. Lett. 90, 052503 (2007); http://dx.doi.org/10.1063/1.2436715 (3 pages) | Cited 2 times

Online Publication Date: 29 January 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The spin-valve phototransistor is a semiconductor-ferromagnetic metal multilayer-semiconductor transistor operated by photoexciting hot electrons in the emitter semiconductor into a Schottky collector. This device uses an ultra-high vacuum-bonded float zone Si/multilayer/n-InP structure. To distinguish the emitter interband-excited component of collector current from base/collector internal photoemission, a lock-in spectroscopy sensitive only to the magnetocurrent is used. The experimental results indicate a pathway to improve the magnetocurrent of a related device, the spin-valve photodiode, by increasing the fraction of hot electron current that travels through both layers of the ferromagnetic spin valve and demonstrate that hot electrons photogenerated in one semiconductor can be collected by another through a thin ferromagnetic multilayer.
Show PACS
85.60.Dw Photodiodes; phototransistors; photoresistors
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
85.30.Tv Field effect devices
73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions

High TC ferromagnetism of Zn(1−x)CoxO diluted magnetic semiconductors grown by oxygen plasma-assisted molecular beam epitaxy

G. L. Liu, Q. Cao, J. X. Deng, P. F. Xing, Y. F. Tian, Y. X. Chen, S. S. Yan, and L. M. Mei

Appl. Phys. Lett. 90, 052504 (2007); http://dx.doi.org/10.1063/1.2437111 (3 pages) | Cited 22 times

Online Publication Date: 31 January 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Co-doped wurtzite ZnO [Zn(1−x)CoxO] thin films have been grown on Al2O3(0001) substrates by using oxygen plasma-assisted molecular beam epitaxy at the low growth temperature of 450 °C. The epitaxial films of Co concentration at 0 ⩽ x ⩽ 0.12 are single crystalline, which were examined by reflection high energy electron diffraction and x-ray diffraction. Both of optical transmission spectrum and in situ. x-ray photoelectron spectroscopy studies confirmed the incorporation of Co2+ cations into wurtzite ZnO lattice. Magnetic measurements revealed that the Zn(1−x)CoxO thin films are ferromagnetic with Curie temperature TC above room temperature, and the ferromagnetism shows intrinsic characteristic.
Show PACS
68.55.-a Thin film structure and morphology
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
78.66.Hf II-VI semiconductors

High resolution transmission electron microscopy and Raman scattering studies of room temperature ferromagnetic Ni-doped ZnO nanocrystals

Hao Wang, Y. Chen, H. B. Wang, C. Zhang, F. J. Yang, J. X. Duan, C. P. Yang, Y. M. Xu, M. J. Zhou, and Q. Li

Appl. Phys. Lett. 90, 052505 (2007); http://dx.doi.org/10.1063/1.2435606 (3 pages) | Cited 27 times

Online Publication Date: 31 January 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Ni-doped ZnO nanocrystals have been synthesized by a wet chemical reaction. The nanocrystals have been investigated carefully by high resolution transmission electron microscopy and all the particles are found to be the known wurtzite ZnO. X-ray photoelectron spectroscopy and Raman spectra results provide the evidence that Ni2+ is incorporated into the ZnO lattice at Zn2+ site. Magnetic property measurements reveal that the as-grown Zn1−xNixO nanocrystals exhibit room temperature ferromagnetic behaviors with saturation magnetization of 0.01 emu/g and Curie temperature above 340 K for Ni concentration of ∼ 1% in atomic ratio.
Show PACS
75.50.Pp Magnetic semiconductors
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.30.Hv Other nonmetallic inorganics
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Tt Fine-particle systems; nanocrystalline materials
79.60.Bm Clean metal, semiconductor, and insulator surfaces

Large intrinsic effect of axial strain on the critical current of high-temperature superconductors for electric power applications

D. C. van der Laan and J. W. Ekin

Appl. Phys. Lett. 90, 052506 (2007); http://dx.doi.org/10.1063/1.2435612 (3 pages) | Cited 35 times

Online Publication Date: 31 January 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A remarkably large reversible reduction in the critical current of “second generation” high-temperature superconductors for electric power applications has been measured with a new technique over a wide range of mechanical strain. The effect amounts to a 40% reduction in critical current at 1% compressive strain in self-magnetic field, and is symmetric for compressive and tensile strains. The intrinsic effect is measured in highly aligned multigranular YBa2Cu3O7−d coated conductors made by different processes, including superconductors with nanoscale pinning centers. This effect and its magnitude are expected to have a significant impact on power applications and provide a useful new parameter for probing the fundamental nature of current transport in high-temperature superconductors.
Show PACS
74.25.Sv Critical currents
74.72.-h Cuprate superconductors
74.25.Ld Mechanical and acoustical properties, elasticity, and ultrasonic attenuation

Decrease of Tc and persistent two gaps upon enhancement of the Ca doping in MgB2 superconductor

Yaxin Sun, Dongli Yu, Zhongyuan Liu, Julong He, Xiangyi Zhang, Yongjun Tian, Jianyong Xiang, and Dongning Zheng

Appl. Phys. Lett. 90, 052507 (2007); http://dx.doi.org/10.1063/1.2435711 (3 pages) | Cited 8 times

Online Publication Date: 31 January 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Superconducting properties have been investigated in the Ca-doped MgB2 (Mg1−xCaxB2) superconductors, which have been synthesized under high temperature and pressure. With increasing doping level x, a linear drop of the critical temperature Tc is observed, and the gap Δσ keeps nearly fixed and the gap Δπ deceases, giving rise to the persistent two-gap feature in the Mg1−xCaxB2 samples for x up to 0.07. Both the Sommerfeld constant γn and the relative weight γπ/γn are found to decrease with raising x, indicative of the decrease of Nπ(0).
Show PACS
74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.62.Dh Effects of crystal defects, doping and substitution
74.25.Jb Electronic structure (photoemission, etc.)

Magnetic and transport properties of homogeneous MnxGe1−x ferromagnetic semiconductor with high Mn concentration

Y. X. Chen, Shi-shen Yan, Y. Fang, Y. F. Tian, S. Q. Xiao, G. L. Liu, Y. H. Liu, and L. M. Mei

Appl. Phys. Lett. 90, 052508 (2007); http://dx.doi.org/10.1063/1.2436710 (3 pages) | Cited 13 times

Online Publication Date: 1 February 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Homogeneous MnxGe1−x ferromagnetic semiconductor films with high Mn concentration were prepared, contrasting with dilute inhomogeneous MnxGe1−x magnetic semiconductors. The saturation magnetization of Mn0.57Ge0.43 films is high, up to 327 emu/cm3 (1.04μB/Mn) at 5 K, and the Curie temperature is about 213 K. The Mn0.57Ge0.43 films show semiconducting resistance, but the magnetoresistance is negligibly small. The anomalous Hall effect was observed below the Curie temperature, which is consistent with the magnetic measurements. The global ferromagnetism was discussed based on s,p-d exchange coupling between the weakly localized s,p hole carriers and the strongly localized d electrons of the Mn atoms.
Show PACS
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
73.61.Le Other inorganic semiconductors
75.50.Pp Magnetic semiconductors
75.50.Cc Other ferromagnetic metals and alloys
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
72.20.My Galvanomagnetic and other magnetotransport effects
75.30.Et Exchange and superexchange interactions

Enhanced magnetocaloric response in Cr/Mo containing Nanoperm-type amorphous alloys

V. Franco, C. F. Conde, A. Conde, and L. F. Kiss

Appl. Phys. Lett. 90, 052509 (2007); http://dx.doi.org/10.1063/1.2437659 (3 pages) | Cited 29 times

Online Publication Date: 1 February 2007

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The magnetocaloric effect of Fe76Cr8−xMoxCu1B15 (x = 0,4) alloys is studied. Although the combined addition of Cr and Mo is more efficient in tuning the Curie temperature of the alloy, the Mo-free alloy presents a higher magnetocaloric response. The refrigerant capacity (RC) for the Mo-containing alloy is comparable to that of Gd5Ge1.9Si2Fe0.1 (for a field of 50 kOe, RC = 273 J kg−1 for the Mo alloy vs 240 J kg−1 for the Gd-based one), with a larger temperature span of the optimal refrigeration cycle (250 K vs 90 K, respectively). The restriction of the temperature span to 90 K gives RC = 187 J kg−1 for the Mo alloy. A master curve behavior for the magnetic entropy change is also evidenced.
Show PACS
75.30.Sg Magnetocaloric effect, magnetic cooling
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Bb Fe and its alloys
65.40.G- Other thermodynamical quantities
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close