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2 Dec 1996

Volume 69, Issue 23, pp. 3453-3607

Page 2 of 3 Pages Previous Page Next Page | Jump to Page

Submicron and low‐temperature ohmic contacts on δ‐doped GaAs

P. J. A. Piotrowicz, J. M. C. England, J. R. A. Cleaver, C. R. Stanley, and M. C. Holland

Appl. Phys. Lett. 69, 3528 (1996); http://dx.doi.org/10.1063/1.117234 (3 pages) | Cited 1 time

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Practical nonalloyed ohmic contacts on δ‐doped GaAs have been compared for AuGeNi (88:12:5) /and Cr metallizations to show the importance of metallization type for minimizing the contact resistance. They are shown to have low contact resistances even at 4.2 K and for contact sizes down to 240 nm diam. The effect of heating AuGeNi contacts to 270 °C is shown to be beneficial for large‐area contacts but not for submicron contacts, implying that nonuniformity is introduced. © 1996 American Institute of Physics.
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73.40.Cg Contact resistance, contact potential
85.40.Ls Metallization, contacts, interconnects; device isolation

InAs channel heterostructure‐field effect transistors with InAs/AlSb short‐period superlattice barriers

C. R. Bolognesi, J. E. Bryce, and D. H. Chow

Appl. Phys. Lett. 69, 3531 (1996); http://dx.doi.org/10.1063/1.117235 (3 pages) | Cited 5 times

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We report on the implementation of InAs‐channel heterostructure‐field‐effect transistors (HFETs) fabricated with InAs/AlSb short‐period superlattice barriers. The InAs/AlSb superlattice barrier structure is advantageous for InAs/AlSb HFETs because of its improved chemical stability against oxidation when compared to pure AlSb, and its compatibility with silicon as an n‐type dopant during growth by molecular beam epitaxy. The structures examined here consist of a 200‐Å‐wide InAs quantum well inserted between 25/25 Å InAs/AlSb superlattice barriers that provide a 0.5 eV conduction band discontinuity between the quantum well and the superlattice barrier. Fabricated HFET devices display complete channel modulation, confirming the field‐effect operation at room temperature. In addition, we demonstrate the modulation doping of an InAs quantum well clad by silicon‐doped InAs/AlSb superlattice barriers. © 1996 American Institute of Physics.
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85.30.Tv Field effect devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Recrystallization of MeV Si implanted 6H‐SiC

Shinsuke Harada, Manabu Ishimaru, Teruaki Motooka, Toshitake Nakata, Tomoaki Yoneda, and Morio Inoue

Appl. Phys. Lett. 69, 3534 (1996); http://dx.doi.org/10.1063/1.117236 (3 pages) | Cited 10 times

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Microstructures of recrystallized layers in 8 MeV Si3+ ion implanted 6‐H‐SiC (0001) wafers have been characterized by means of transmission electron microscopy. Epitaxial recrystallization of buried amorphous layers was observed at annealing temperature as low as 1000 °C. Layer‐by‐layer epitaxy of 6H‐SiC initially occurred and it was changed to columnar growth when layer‐by‐layer growth exceeded 100 nm in thickness. From the microdiffraction analysis, it was found that the columnar regions are defected 6H‐SiC with crystal orientations different from the substrate. In addition to 6H‐SiC, epitaxial 3C‐SiC was also confirmed in the recrystallized layer. Based on these results, we have proposed a structure model of the recrystallized layer in which stacking faults in the columnar regions are induced by mismatched connections between the columnar and layered 6H‐SiC regions. © 1996 American Institute of Physics.
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68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.37.Lp Transmission electron microscopy (TEM)
68.55.-a Thin film structure and morphology
81.15.Np Solid phase epitaxy; growth from solid phases

Schottky barriers and contact resistances on p‐type GaN

T. Mori, T. Kozawa, T. Ohwaki, Y. Taga, S. Nagai, S. Yamasaki, S. Asami, N. Shibata, and M. Koike

Appl. Phys. Lett. 69, 3537 (1996); http://dx.doi.org/10.1063/1.117237 (3 pages) | Cited 91 times

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We measured the Schottky barrier heights and specific contact resistivities of four different metals on p‐type GaN. The Schottky barrier heights of Pt, Ni, Au, and Ti were obtained from the current‐voltage characteristics to be 0.50, 0.50, 0.57, and 0.65 eV, respectively. The specific contact resistivities were 0.013, 0.015, 0.026, and 0.035 Ω⋅cm2, respectively. Our experimental results proved that the Schottky barrier heights and specific contact resistivities decrease with increase in metal work function as expected theoretically. © 1996 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Cg Contact resistance, contact potential
73.61.Ey III-V semiconductors

High‐frequency capacitance resonance of ZnO‐based varistor ceramics

S. Ezhilvalavan and T. R. N. Kutty

Appl. Phys. Lett. 69, 3540 (1996); http://dx.doi.org/10.1063/1.117238 (3 pages) | Cited 9 times

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Capacitance resonance of ZnO varistor ceramics can be shifted from gegahertz to a few megahertz frequency region with increasing amounts of specific secondary phases. The observed resonance is due to the total inductance of the varistor ceramics wherein the grain boundaries are shorted at high frequencies, which arises from the dynamic exchange of charge carriers at the grain interiors and the trap states that are formed at the depletion regions around the grain boundaries. This is applicable to ZnO/ZnO grain boundaries as also to ZnO/secondary phase boundaries. The capacitance‐voltage studies show direct correlation between the magnitude of capacitance resonance and the nonlinearity coefficient in current‐voltage relations. © 1996 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
84.32.Ff Conductors, resistors (including thermistors, varistors, and photoresistors)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
72.80.Sk Insulators

PdIn contacts to n‐type and p‐type GaP

C. ‐F. Lin, D. B. Ingerly, and Y. A. Chang

Appl. Phys. Lett. 69, 3543 (1996); http://dx.doi.org/10.1063/1.117239 (3 pages) | Cited 6 times

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PdIn was used as a contact material to n‐type and p‐type GaP. On n‐type GaP it forms a low resistance ohmic contact upon rapid thermal annealing. PdIn/n‐GaP (S doped at 2–3 ×1018 cm−3) contacts annealed at 600 °C for 1 min had specific contact resistance’s lower than 1×10−4 Ω cm2. Unlike the contacts to n‐GaP, PdIn contacts to p‐GaP (Zn doped 1–2×1018 cm−3) show rectifying behavior at all annealing conditions. However, the effective Schottky barrier height seems to decrease significantly with thermal annealing. In addition to the electrical measurements, glancing angle x‐ray diffraction was used to characterize the contacts. The glancing angle x‐ray diffusion pattern of PdIn/n‐GaP, annealed at 600 °C for 1 min, is consistent with the formation of an (InyGa1−y)P phase due to the thermal annealing. The ohmic behavior of the PdIn contacts to n‐type GaP and the decrease in the contact’s Schottky barrier height on p‐type GaP is attributed to the formation of this (InyGa1−y)P phase at the contact’s interface. © 1996 American Institute of Physics.
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
68.35.Fx Diffusion; interface formation
61.05.cm X-ray reflectometry (surfaces, interfaces, films)

Evidence for the role of the surface potential and native oxide on thermal properties of crystalline Si

Shailendra Kumar

Appl. Phys. Lett. 69, 3546 (1996); http://dx.doi.org/10.1063/1.117240 (3 pages)

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Thermal properties of crystalline Si have been studied using the photopyroelectric (PPE) technique in the temperature range 100–300 K. It has been observed that the generation and propagation of the thermal waves in Si depends upon the thermal history of the sample. The native amorphous silicon dioxide layer on Si and the surface potential affect the propagation of the thermal waves and this effect is not reversible in the temperature range 150 K<T<260 K. It is observed that the contactless PPE technique can also be used to study recombination processes of excess carriers in semiconductors. © 1996 American Institute of Physics.
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66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
68.60.Dv Thermal stability; thermal effects
73.25.+i Surface conductivity and carrier phenomena

Study of the ground state splitting of N–O complexes in Cz–Si grown under nitrogen atmosphere

X. H. Shi, P. L. Liu, and S. C. Shen

Appl. Phys. Lett. 69, 3549 (1996); http://dx.doi.org/10.1063/1.117241 (2 pages) | Cited 1 time

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Far‐infrared absorption spectra of Cz–Si grown under a reduced pressure of high pure nitrogen atmosphere have been investigated at different temperatures. Seven new series of lines resulting from the ground state splitting of N–O complexes [D(N–O)s] have been observed. The results indicate that the D(N–O)s have different structures. In addition, according to effective mass approximation, the binding energies of the split ground states have been obtained. © 1996 American Institute of Physics.
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71.55.Cn Elemental semiconductors
78.30.Am Elemental semiconductors and insulators
81.10.Fq Growth from melts; zone melting and refining

Inhibited oxidation in low‐temperature grown GaAs surface layers observed by photoelectron spectroscopy

T.‐B. Ng, D. B. Janes, D. McInturff, and J. M. Woodall

Appl. Phys. Lett. 69, 3551 (1996); http://dx.doi.org/10.1063/1.117242 (3 pages) | Cited 18 times

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The surface oxidation characteristics of a GaAs layer structure consisting of a thin (10 nm) layer of low‐temperature‐grown GaAs (LTG:GaAs) on a heavily n‐doped GaAs layer, both grown by molecular beam epitaxy, have been studied using x‐ray photoelectron spectroscopy (XPS). Between the layer growth and XPS characterization, the unannealed LTG:GaAs sample and a control sample without the LTG:GaAs surface layer were exposed to the atmosphere. The rate of surface oxidation in the sample with a LTG:GaAs surface layer was significantly lower than the oxidation rate of the control sample. This direct observation of inhibited oxidation confirms the surface stability of comparable structures inferred from earlier electrical measurements. The inhibited surface oxidation rate is attributed to the bulk Fermi‐level pinning and the low minority carrier lifetime in unannealed LTG:GaAs. © 1996 American Institute of Physics.
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73.25.+i Surface conductivity and carrier phenomena
81.65.Mq Oxidation
79.60.Dp Adsorbed layers and thin films

Carrier dynamics in InP with metallic precipitates

S. Marcinkevičius, A. Krotkus, R. Adomavičius, R. Leon, and C. Jagadish

Appl. Phys. Lett. 69, 3554 (1996); http://dx.doi.org/10.1063/1.117243 (3 pages) | Cited 6 times

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Time‐resolved photoluminescence and photoconductivity studies were performed on InP with nanometer‐size metallic precipitates. InP samples with precipitates had been prepared by Cu diffusion and subsequent quenching. The carrier lifetimes for minority holes and majority electrons have been found to be of the order of tens of picoseconds and a nanosecond, respectively. Observed reduction of nonequilibrium carrier trapping times and temporal changes of the photoluminescence spectra are attributed to the effects of the built‐in electric fields in the space–charge regions around metallic precipitates. © 1996 American Institute of Physics.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.47.-p Spectroscopy of solid state dynamics
81.30.Mh Solid-phase precipitation
72.80.Ey III-V and II-VI semiconductors

Rectification properties and interface states of heterojunctions between solid C60 and n‐type GaAs

K. M. Chen, Y. X. Zhang, G. G. Qin, S. X. Jin, K. Wu, C. Y. Li, Z. N. Gu, and X. H. Zhou

Appl. Phys. Lett. 69, 3557 (1996); http://dx.doi.org/10.1063/1.117244 (3 pages) | Cited 10 times

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Solid C60/n‐GaAs heterojunctions have been fabricated by deposition of solid C60 film on the (100)‐oriented epitaxial n‐type GaAs substrates and their electrical characteristics have been measured. The rectification ratio is greater than 106 at a bias of ±1 V. The current for a fixed forward bias is an exponential function of reciprocal temperature, from which the effective potential barrier height of the heterojunction is determined to be 0.58 eV. A trap with an energy level 0.35 eV below the conduction band of GaAs at the C60/GaAs interface has been observed by the deep level transient spectroscopy technique. © 1996 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Ei Rectification
73.20.At Surface states, band structure, electron density of states
72.80.Rj Fullerenes and related materials

Low resistivity copper germanide on (100) Si for contacts and interconnections

M. A. Borek, S. Oktyabrsky, M. O. Aboelfotoh, and J. Narayan

Appl. Phys. Lett. 69, 3560 (1996); http://dx.doi.org/10.1063/1.117245 (3 pages) | Cited 5 times

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We have deposited thin films of Cu3Ge on (100) Si by the sequential e‐beam deposition of an amorphous Ge layer followed by a polycrystalline Cu layer. The films were then annealed in flowing N2 for 30 min over a temperature range of 150–600 °C to induce complete recrystallization of the Cu–Ge films. Films of Cu3Ge form a smooth, atomically sharp interface with (100) Si over a wide range of anneal temperatures, as determined by transmission electron microscopy, indicating the lack of any chemical reactions, i.e., compound formation, at the film/substrate interface. We have observed by secondary ion mass spectrometry, that a substantial amount of Si has diffused into the Cu–Ge in varying amounts that exhibit strong dependence on the anneal temperature. Despite the large amount of Si that has diffused into the films, the Cu3Ge maintains its low resistivity (ρ=10–15 μΩ cm) up to an anneal temperature of 600 °C, at which point the film completely loses its structural integrity, i.e., it becomes discontinuous with the formation of complex compounds. These results show that Cu3Ge represents a potential candidate material for contact and metallization for next generation Si‐based semiconductor devices. © 1996 American Institute of Physics.
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73.61.At Metal and metallic alloys
85.40.Ls Metallization, contacts, interconnects; device isolation

Ohmic contacts to n‐type silicon‐germanium

S. F. Nelson and T. N. Jackson

Appl. Phys. Lett. 69, 3563 (1996); http://dx.doi.org/10.1063/1.117246 (3 pages) | Cited 1 time

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We have studied both alloyed metal and ion‐implanted Ohmic contacts to n‐type silicon/silicon germanium heterostructures. We found that gold/antimony contacts can distort low temperature mobility measurements, and seriously degrade a sample after a short time. A more reliable alternative alloy is silver/antimony. We also found phosphorous ion‐implanted contacts, annealed to 600 °C for 30 min, to be reliably Ohmic and of low resistivity at low temperatures. © 1996 American Institute of Physics.
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73.40.Cg Contact resistance, contact potential
73.61.Cw Elemental semiconductors
85.40.Ls Metallization, contacts, interconnects; device isolation

High quality GaN–InGaN heterostructures grown on (111) silicon substrates

J. W. Yang, C. J. Sun, Q. Chen, M. Z. Anwar, M. Asif Khan, S. A. Nikishin, G. A. Seryogin, A. V. Osinsky, L. Chernyak, H. Temkin, Chimin Hu, and S. Mahajan

Appl. Phys. Lett. 69, 3566 (1996); http://dx.doi.org/10.1063/1.117247 (3 pages) | Cited 48 times

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We report on the low pressure metal organic chemical vapor deposition of single crystal, wurtzitic layers of GaN and GaN/InGaN heterostructures on (111) GaAs/Si composite substrates. The structural, optical, and electrical properties of the epitaxial layers are evaluated using x‐ray diffraction, transmission electron microscopy, photoluminescence, and measurements of minority carrier diffusion length. These measurements demonstrate high quality of GaN grown on the composite substrate. © 1996 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.55.Cr III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Detection of terahertz radiation by hot electron effects in coupled quantum well photodiodes

R. J. Stone, J. G. Michels, S. L. Wong, C. T. Foxon, R. J. Nicholas, and A. M. Fox

Appl. Phys. Lett. 69, 3569 (1996); http://dx.doi.org/10.1063/1.117248 (3 pages) | Cited 7 times

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Detection of continuous‐wave terahertz (THz) radiation has been demonstrated in GaAs/AlGaAs coupled quantum well p‐i‐n photodiodes by intrasubband absorption. The sharp interwell tunneling resonances observed in the photocurrent are highly sensitive to temperature, and the carrier temperature increase caused by the absorption of THz radiation is found to affect the photocurrent in a qualitatively similar manner. We find that the effect results in detectivities of THz radiation around 1 mA/W for a photocurrent signal of 100 nA. We discuss the functionality of our device in the context of an ‘‘optical/THz mixer,’’ where the mixing occurs between the modulation frequencies of the applied THz and visible light fields. © 1996 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Disordering of the ZnCdSe single quantum well structure by Cd diffusion

M. Momose, A. Taike, M. Kawata, J. Gotoh, and S. Nakatsuka

Appl. Phys. Lett. 69, 3572 (1996); http://dx.doi.org/10.1063/1.117210 (3 pages) | Cited 6 times

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The effects of annealing on a ZnCdSe single quantum well (SQW) structure with ZnCdSSe/ZnSSe superlattice optical guiding layers are investigated. X‐ray diffraction and photoluminescence (PL) measurements showed disordering of a ZnCdSSe/ZnSSe superlattice after annealing at about 500 °C. The PL peak energy of the SQW shifted to the higher energy side, and the linewidth narrowed in the sample annealed at 300 °C. Cadmium diffusion was confirmed by secondary ion mass spectrometry. We found that the disordering of the ZnCdSSe/ZnSSe superlattice and the changes in the emissions from the SQW were due to the Cd diffusion. © 1996 American Institute of Physics.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
66.30.Ny Chemical interdiffusion; diffusion barriers
78.66.Hf II-VI semiconductors

Transient subpicosecond Raman studies of electron velocity overshoot in an InP p‐i‐n nanostructure semiconductor

K. T. Tsen, D. K. Ferry, Jye‐Shyang Wang, Chao‐Hsiung Huang, and Hao‐Hsiung Lin

Appl. Phys. Lett. 69, 3575 (1996); http://dx.doi.org/10.1063/1.117211 (3 pages) | Cited 7 times

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Transient electron transport in an InP p‐i‐n nanostructure semiconductor has been studied by subpicosecond Raman spectroscopy at T=300 K. Both the nonequilibrium electron distribution and electron drift velocity in the regime of electron velocity overshoot have been directly measured. It is demonstrated that electron drift velocity in an InP p‐i‐n nanostructure is significantly larger than that in a GaAs p‐i‐n nanostructure sample, as a result of the larger central to satellite valley energy separation in InP. © 1996 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.30.Fs III-V and II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics

InGaAs metal‐semiconductor‐metal photodetectors with engineered Schottky barrier heights

W. A. Wohlmuth, M. Arafa, A. Mahajan, P. Fay, and I. Adesida

Appl. Phys. Lett. 69, 3578 (1996); http://dx.doi.org/10.1063/1.117212 (3 pages) | Cited 10 times

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An InAlAs/InGaAs/InP metal‐semiconductor‐metal photodetector with engineered Schottky barrier heights has been fabricated. A significant decrease in dark current with no change in the responsivity or the bandwidth was obtained by independently engineering the Schottky barrier heights at the anode and cathode. These photodiodes with an electrode width and spacing of 2 μm exhibited a dark current density of 20.0 fA/μm2 at an applied bias of 5 V. This dark current density is ∼6 times lower than the previously reported minimum. © 1996 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Sx Metal-semiconductor-metal structures
85.60.Gz Photodetectors (including infrared and CCD detectors)

Effect of interdiffusion of quantum well infrared photodetector

Alex S. W. Lee and E. Herbert Li

Appl. Phys. Lett. 69, 3581 (1996); http://dx.doi.org/10.1063/1.117213 (3 pages) | Cited 18 times

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The intersubband infrared photodetector performance is theoretically analyzed for various stages of interdiffusion in AlGaAs/GaAs quantum well. The absorption strength and responsivity are enhanced for certain extents of interdiffusion and the peak detection wavelength red shifts continuously with a large tunable range from 7 to 38.4 μm. The dark current is at an acceptable value for small diffusion extent. © 1996 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
78.66.Fd III-V semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers

A combined Mössbauer and Rutherford backscattering spectroscopy analysis of the influence of nanosized cavities on CoSi2 formation

W. Deweerd, R. Moons, J. Verheyden, K. Milants, G. Langouche, and H. Pattyn

Appl. Phys. Lett. 69, 3584 (1996); http://dx.doi.org/10.1063/1.117214 (3 pages) | Cited 2 times

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For Co in Si, the competition between CoSi2 formation and cavity trapping is studied by Rutherford backscattering and Mössbauer spectroscopy. The presence of nanosized voids hampers the formation of a buried epitaxial silicide layer in its initial phase, preventing the small CoSi2 particles from forming a bulk layer. The Mössbauer spectra show that a pre‐existing silicide phase can be partially dissolved in favor of cavity trapping. In addition, channeling measurements provide qualitative information about the voids, showing that the thermal stability of the voids is much higher than for defects resulting from self‐implantation. © 1996 American Institute of Physics.
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76.80.+y Mössbauer effect; other γ-ray spectroscopy
61.85.+p Channeling phenomena (blocking, energy loss, etc.)
61.72.Qq Microscopic defects (voids, inclusions, etc.)
61.72.Yx Interaction between different crystal defects; gettering effect

Investigation of transverse Peltier effect on top‐seeded melt textureYBa2Cu3O7−δ

Z. H. He, Z. G. Ma, Q. Y. Li, Y. Y. Luo, J. X. Zhang, R. L. Meng, and C. W. Chu

Appl. Phys. Lett. 69, 3587 (1996); http://dx.doi.org/10.1063/1.117215 (3 pages) | Cited 5 times

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The transverse Peltier effect is investigated on the top‐seeded melt texture superconductor YBa2Cu3O7−δ (YBCO). By restricting the heat absorbing or evolving on one of the sample’s surfaces, the Peltier heat flow is converted into a temperature difference for measurement. The temperature difference is found proportional to the current applied, which is in accordance with the prediction of transverse Peltier effect. Based on a simplified model, the difference of the Seebeck coefficients between the ab plane and the c axis, ∣Sab−Sc∣, is about 35 μV/K. It is in good agreement with that of large single crystal [I. Terasaki, Y. Sato, S. Tajima, S. Miyamoto, and S. Tanaka, Physica C 235‐240, 1413 (1994)]. The transverse Peltier effect is verified. This supports the idea that the off‐diagonal thermoelectric effect is responsible for the anomalously high laser‐induced transient transverse voltage on the oriented YBCO superconducting thin films. © 1996 American Institute of Physics.
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74.25.F- Transport properties
74.72.-h Cuprate superconductors

Magneto‐optic observation of anomalous Meissner current flow in superconducting thin films with slits

M. Baziljevich, T. H. Johansen, H. Bratsberg, Y. Shen, and P. Vase

Appl. Phys. Lett. 69, 3590 (1996); http://dx.doi.org/10.1063/1.117216 (3 pages) | Cited 13 times

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Slits patterned into a YBa2Cu3O7−δ thin film were observed to obstruct Meissner sheet currents leading to an imbalance in the local Meissner screening properties. The new phenomenon was studied with magneto‐optic imaging where twin lobes of opposite flux polarity were seen to form near the slits and inside the Meissner region. The lobe closest to the sample edge is always polarized opposite to the applied field. At weak fields, the anomalous flux generation is reversible. At higher fields, but still sufficiently small to keep the vortex penetration front away from the slits, the anomalous current starts nucleating flux lines which become trapped when the field is removed. © 1996 American Institute of Physics.
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74.78.-w Superconducting films and low-dimensional structures
74.25.Ha Magnetic properties including vortex structures and related phenomena
78.20.Jq Electro-optical effects

NiMn‐pinned spin valves with high pinning field made by ion beam sputtering

S. Mao, S. Gangopadhyay, N. Amin, and E. Murdock

Appl. Phys. Lett. 69, 3593 (1996); http://dx.doi.org/10.1063/1.117217 (3 pages) | Cited 40 times

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Spin valves of film layer structure, Ta/NiMn/NiFe/Co/Cu/Co/NiFe/Ta/Substrate were fabricated by ion beam sputtering. Optimization of the processes of deposition and posthermal treatment yields highly (111) oriented spin valve films with a giant‐magnetoresistance ratio of above 4% and pinning field of 650 Oe. This is the strongest pinning field ever observed. It stays constant up to 180 °C, then decreases to zero at a blocking temperature of 380 °C. These spin valves are highly thermally stable and, thus, suitable for the application of high density recording heads. © 1996 American Institute of Physics.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Ss Magnetic recording materials
75.47.De Giant magnetoresistance
81.15.Cd Deposition by sputtering

Magnetocaloric effect in La0.67Ca0.33MnOδ and La0.60Y0.07Ca0.33MnOδ bulk materials

X. X. Zhang, J. Tejada, Y. Xin, G. F. Sun, K. W. Wong, and X. Bohigas

Appl. Phys. Lett. 69, 3596 (1996); http://dx.doi.org/10.1063/1.117218 (3 pages) | Cited 83 times

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The dependence of magnetization on the applied magnetic field and temperature was measured carefully near their Curie temperatures for two perovskite manganite samples: La0.67Ca0.33MnOδ and La0.60Y0.07Ca0.33MnOδ. It is suggested by the results that these materials can be utilized as both the thermal storage (passive regeneration) and as the working material (active regeneration) in an active magnetic regenerative refrigerator with very large temperature span, for their significant entropy change upon the application of a magnetic field and the easily tuned Curie temperatures. © 1996 American Institute of Physics.
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75.30.Sg Magnetocaloric effect, magnetic cooling
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Effect of trivalent ion composition on the magnetoresistance behavior of LaxNd0.6−xSr0.40MnO3−δ films

Wei Zhang, Ian W. Boyd, Martin Elliott, and William Herrenden‐Harkerand

Appl. Phys. Lett. 69, 3599 (1996); http://dx.doi.org/10.1063/1.117219 (3 pages) | Cited 2 times

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The effect of trivalent ion composition (x) on the transport properties and magnetoresistance (MR) behavior of LaxNd0.6−xSr0.40MnO3−δ films (0.15≤x≤0.45) grown on Si(100) substrates by pulsed laser deposition is reported. It is found that the temperature associated with the peak resistivity can be shifted to higher values by varying the trivalent ion composition, in a similar way to that earlier observed in divalent substituted La1−xMxMnO3−δ (M=Ba, Sr, Ca, Pb) films. MR values near room temperature under a magnetic field of 4.7 T increase with lanthanum ion composition, and the largest MR value of around 30% (Δρ/ρH) appeared in films with x=0.45. Our results suggest that these effects are primarily related to an increase of the Curie temperature of the films as a result of lattice expansion by partial substitution of neodymium with lanthanum, which has a larger ionic radius. © 1996 American Institute of Physics.
Show PACS
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.47.De Giant magnetoresistance
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ss Magnetic recording materials
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