jap banner
  • 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 Dec 1999

Volume 86, Issue 11, pp. 5927-6612

Return to All Sections
back to top
RSS Feeds

Thermal stability of plasma deposited thin films of hydrogenated carbon–nitrogen alloys

J. V. Anguita, S. R. P. Silva, A. P. Burden, B. J. Sealy, S. Haq, M. Hebbron, I. Sturland, and A. Pritchard

J. Appl. Phys. 86, 6276 (1999); http://dx.doi.org/10.1063/1.371685 (6 pages) | Cited 18 times

Full Text: | Download PDF

Show Abstract
The need to grow high quality semiconducting hydrogenated amorphous carbon (a-C:H) thin films to allow n-type electronic doping by nitrogenation has lead us to deposit films with low paramagnetic defect density (1017 cm−3). The films were grown on the earthed electrode of a radio frequency driven plasma enhanced chemical vapor deposition system using methane, helium and a range of nitrogen concentrations as the precursor gases. The deposited films are shown to be polymer like. Changes in the chemical structure and relative bond fractions as a function of the nitrogen flow rate into the plasma chamber and ex situ annealing are reported. Particular attention is paid to changes in the film structure after annealing at 100 °C, since an increase in the E04 optical band gap is observed as a function of nitrogen flow after the anneal. This suggests a decrease in the defect density of the film. © 1999 American Institute of Physics.
Show PACS
68.60.Dv Thermal stability; thermal effects
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
71.23.Cq Amorphous semiconductors, metallic glasses, glasses
78.66.Jg Amorphous semiconductors; glasses
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Gc Amorphous semiconductors

Contactless characterization of melt-textured superconducting junctions using micro-Hall sensor arrays

Goran Karapetrov, Vladimir Cambel, W. K. Kwok, R. Nikolova, G. W. Crabtree, H. Zheng, and B. W. Veal

J. Appl. Phys. 86, 6282 (1999); http://dx.doi.org/10.1063/1.371686 (5 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
We use spatially resolved Hall-probe magnetometry and magneto-optical imaging to study current-carrying properties of melt-textured high-temperature superconducting welds at high magnetic fields. Magneto-optical images show no deterioration of the current-carrying properties of the sample in the presence of the superconducting weld. The study of the vortex dynamics near the junction using high-resolution Hall-probe magnetometry revealed enhanced relaxation of the magnetization at the junction at high temperatures. We attribute this behavior to an increased local concentration of defects near the weld that, depending on the temperature range, either facilitates enhanced relaxation or strengthens the local pinning properties. © 1999 American Institute of Physics.
Show PACS
74.50.+r Tunneling phenomena; Josephson effects
74.72.-h Cuprate superconductors
74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.25.Ha Magnetic properties including vortex structures and related phenomena
78.20.Ls Magneto-optical effects
74.25.Gz Optical properties

Resistance of a domain wall in La0.7Ca0.3MnO3

N. D. Mathur, P. B. Littlewood, N. K. Todd, S. P. Isaac, B.-S. Teo, D.-J. Kang, E. J. Tarte, Z. H. Barber, J. E. Evetts, and M. G. Blamire

J. Appl. Phys. 86, 6287 (1999); http://dx.doi.org/10.1063/1.371687 (4 pages) | Cited 48 times

Full Text: | Download PDF

Show Abstract
Although colossal magnetoresistance (CMR) materials exhibit large changes in electrical resistance (up to 106%), large magnetic fields (several tesla) must be applied. To obtain a sizeable low-field effect (<102% in several millitesla), it is necessary to incorporate structural discontinuities such as grain boundaries, or other types of interfaces. The potential for applications, however, remains limited because structural discontinuities increase electrical resistance by several orders of magnitude and hence create noise. Moreover, it has proven to be difficult to fabricate structural discontinuities reproducibly. We have attempted to investigate discontinuities that are purely magnetic via transport measurements through a precisely controlled number of magnetic domain walls of known area in thin film devices of the ferromagnetic CMR perovskite La0.7Ca0.3MnO3. A sharp low-field switching seen below ∼110 K is ascribed to the formation of a precise number of magnetic domain walls, each with resistance-area product 8×10−14 Ω m2 at 77 K. This is four orders of magnitude larger than expected, suggesting that the domain walls contain an additional structure. Our findings demonstrate that CMR devices are capable of low-noise low-field switching, and suggest the possibility of exploiting a hitherto unexpected intrinsic effect reproducibly and therefore commercially. © 1999 American Institute of Physics.
Show PACS
75.47.Gk Colossal magnetoresistance
75.50.Dd Nonmetallic ferromagnetic materials
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ch Domain walls and domain structure
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.47.De Giant magnetoresistance

Field-dependence of quantum tunneling in small antiferromagnetic particles

Gwang-Hee Kim

J. Appl. Phys. 86, 6291 (1999); http://dx.doi.org/10.1063/1.371688 (4 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
The quantum tunneling of small antiferromagnetic particle is studied in the presence of an external magnetic field at an arbitrary angle. It is found that for antiferromagnetic particle with noncompensated sublattices the Wentzel-Kramers-Brillouin exponent and the crossover temperature from the thermal to the quantum regime depend on the direction and strength of the applied field. This features can be tested with the use of existing experimental techniques. © 1999 American Institute of Physics.
Show PACS
75.45.+j Macroscopic quantum phenomena in magnetic systems
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Ee Antiferromagnetics

High pressure effect on magnetic properties and volume anomalies of Ce2Fe17

I. Medvedeva, Z. Arnold, A. Kuchin, and J. Kamarád

J. Appl. Phys. 86, 6295 (1999); http://dx.doi.org/10.1063/1.371689 (6 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
We present the results of high pressure studies of magnetization, magnetic phase transitions, and related volume anomalies for the intermetallic compound Ce2Fe17 under hydrostatic pressures up to 10 kbar. The giant negative pressure effect on the ferromagnetic ordering temperature ΘT = 94 K was determined: dΘT/dP = −(38±2) K/kbar. This extraordinary decrease of ΘT under pressure is not accompanied by the related pronounced decrease of the saturated magnetization under pressure below 2.5 kbar. The effect of pressure on the Néel temperature TN = 206 K is less pronounced: dTN/dP = −(1.7±0.2) K/kbar. A large positive spontaneous volume magnetostriction that is observed below TN is suppressed by the application of high pressure and it disappears above 2.5 kbar. A competition of positive and negative exchange interactions between iron atoms is discussed and is thought to be the main reason for the volume anomalies observed. The role of the f electrons of Ce, their possible hybridization with d states of Fe, and their role in magnetic properties of the Ce2Fe17 compound is not yet clear. © 1999 American Institute of Physics.
Show PACS
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Bb Fe and its alloys
75.50.Ee Antiferromagnetics
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
62.50.-p High-pressure effects in solids and liquids
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Et Exchange and superexchange interactions

Effects of Co addition on magnetic properties and nanocrystallization in amorphous Fe84Zr3.5Nb3.5B8Cu1 alloy

Shuli He, Kaiyuan He, Baogen Shen, Hongwei Zhang, Shaoying Zhang, and Huiqun Guo

J. Appl. Phys. 86, 6301 (1999); http://dx.doi.org/10.1063/1.371690 (4 pages) | Cited 8 times

Full Text: | Download PDF

Show Abstract
The structure, Curie temperature, and magnetization of (Fe1−xCox)84Zr3.5Nb3.5B8Cu1 (x = 0.0–0.8) alloys were investigated by x-ray diffractometer, differential scanning calorimeter, magnetic balance, and extracting sample magnetometer, respectively. The bcc grains are embedded in the amorphous matrix after controlled annealing. The crystallization temperature Tx of the amorphous alloy decreases with the increasing Co content, whereas the Curie temperature Tc of the amorphous alloy is enhanced by an increase in Co content. The magnetization measured under the field of 60 kOe at a temperature of 1.5 K is enhanced first by the increase of Co addition, and exhibits a maximum at the composition where x = 0.2, then decreases while Co content increases. © 1999 American Institute of Physics.
Show PACS
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.-s Critical-point effects, specific heats, short-range order
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.43.Dq Amorphous semiconductors, metals, and alloys
75.50.Bb Fe and its alloys
61.46.-w Structure of nanoscale materials

Thermal decay of ferro/antiferromagnetic exchange coupling in Co/CrMnPt systems

Koichi Nishioka

J. Appl. Phys. 86, 6305 (1999); http://dx.doi.org/10.1063/1.371691 (5 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
To investigate thermal decay of ferro/antiferromagnetic coupling, spin valve films with Co/(Cr0.4Mn0.6)90Pt10 exchange coupling layers were heat treated at various temperatures under a magnetic field whose direction was opposite to the pinning direction, and the pinning fields were evaluated at 35 °C. The pinning field decayed as the treatment time increased. During the first 10 min of the heat treatment, the pinning field decreased rapidly and then decreased gradually. The initial decrease in the pinning field became larger and the rate of the change of the pinning field after 10 min became larger at the higher treatment temperatures. A thermal fluctuation model, which assumes coherent rotations and grain size distributions in the antiferromagnets, was used to obtain the activation energy and relaxation times for reversal of the antiferromagnetic moment. Smaller antiferromagnetic grains had lower activation energies and shorter relaxation times. As a result, the smaller grains reversed their moments at an earlier time stage, which gave rise to the rapid decay of the pinning field during the first 10 min of the heat treatment. The model explains the thermal decay of the pinning field when the temperature is lower than 130 °C. However, a narrower distribution of the activation energy than can be expected from the model is required to explain the thermal decay at 150 °C, which suggests that a incoherent magnetic rotation occurs in antiferromagnets above 150 °C. © 1999 American Institute of Physics.
Show PACS
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.30.Et Exchange and superexchange interactions
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics
75.47.De Giant magnetoresistance

Structure, magnetic properties, and magnetostriction of (Tb1−xNdx)(Fe0.4Co0.6)1.9

Z. J. Guo, S. C. Busbridge, B. W. Wang, Z. D. Zhang, X. G. Zhao, and D. Y. Geng

J. Appl. Phys. 86, 6310 (1999); http://dx.doi.org/10.1063/1.371692 (5 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
The structure and magnetostriction of (Tb1−xNdx)(Fe0.4Co0.6)1.9 (0<x<1) alloys have been investigated at room temperature and the magnetic properties determined over the temperature range 1.5–300 K. It was found that the matrix of (Tb1−xNdx)(Fe0.4Co0.6)1.9 is essentially that of a (Tb,Nd) (Fe,Co)2 phase with a MgCu2-type cubic Laves structure for all values of x. The lattice parameter of the Laves phase increases from 0.7297 to 0.7363 nm as x increases from 0 to 1 and obeys Vegard’s law. We have measured the Curie temperature to decrease with increasing x from 667 K for Tb(Fe0.4Co0.6)Fe1.9 to 454 K for Nd(Fe0.4Co0.6)Fe1.9. The resultant macroscopic magnetization becomes zero when x = 0.45 at a temperature of 1.5 K. At 300 K, a slightly smaller value of x is found to produce no resultant magnetization, and the spontaneous magnetostriction constant λ111 decreases slowly with increasing Nd content and vanishes abruptly from a value of 1630×10−6 when x>0.65. The polycrystalline isofield magnetostriction curves exhibit a minimum at x = 0.45 and a peak at x = 0.65. The observed behavior can be explained on the basis of opposing rare-earth Tb and Nd moments and an anisotropy minimum close to x = 0.65. As the temperature is reduced below 300 K, the spin reorientation occurs at greater Nd concentrations. © 1999 American Institute of Physics.
Show PACS
75.50.Bb Fe and its alloys
75.80.+q Magnetomechanical effects, magnetostriction
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
61.66.Dk Alloys

Heat capacity near first order phase transitions and the magnetocaloric effect: An analysis of the errors, and a case study of Gd5(Si2Ge2) and Dy

V. K. Pecharsky and K. A. Gschneidner

J. Appl. Phys. 86, 6315 (1999); http://dx.doi.org/10.1063/1.371734 (7 pages) | Cited 22 times

Full Text: | Download PDF

Show Abstract
The heat capacity measured in an adiabatic heat pulse calorimeter with nonzero heat capacity suffers from intrinsic errors in the vicinity of a first order phase transition. When these errors are carried over into the calculation of the magnetocaloric effect, the latter also suffers from large systematic errors. The sources of the intrinsic errors in the heat capacity near the first order phase transition temperature and the procedures to minimize them are discussed. The experimental heat capacity data of Gd5(Si2Ge2) and ultra pure Dy, both of which exhibit first order phase transition, are used to confirm the theoretical conclusions. © 1999 American Institute of Physics.
Show PACS
75.30.Sg Magnetocaloric effect, magnetic cooling
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
65.40.-b Thermal properties of crystalline solids
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
06.20.Dk Measurement and error theory
07.20.Fw Calorimeters

Modifying the temperature dependence of magnetic garnet film coercivity by etching

G. Vértesy and B. Keszei

J. Appl. Phys. 86, 6322 (1999); http://dx.doi.org/10.1063/1.371733 (5 pages)

Full Text: | Download PDF

Show Abstract
The temperature dependence of the domain-wall coercive field of epitaxial magnetic garnet films was modified in a defined temperature range by removing the surface layer of the films. Outside the given temperature range the coercivity versus temperature curve did not change. The result supports a model of coercivity according to which different sets of material imperfections are responsible for pinning the domain walls in different temperature regions. Appropriate processing of the samples enables some of the pinning sets to be modified independently of each other. © 1999 American Institute of Physics.
Show PACS
75.50.Gg Ferrimagnetics
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.65.Cf Surface cleaning, etching, patterning

Effect of oxygen content on the structural, transport, and magnetic properties of La1−δMn1−δO3 thin films

Y. G. Zhao, M. Rajeswari, R. C. Srivastava, A. Biswas, S. B. Ogale, D. J. Kang, W. Prellier, Zhiyun Chen, R. L. Greene, and T. Venkatesan

J. Appl. Phys. 86, 6327 (1999); http://dx.doi.org/10.1063/1.371693 (4 pages) | Cited 9 times

Full Text: | Download PDF

Show Abstract
(110) oriented La1−δMn1−δO3 thin films with different oxygen content were grown on (001) LaAlO3 substrates by pulsed laser deposition. Samples prepared in higher oxygen partial pressures show a ferromagnetic transition around 200 K. The transport is thermally activated with a change in slope at the ferromagnetic transition. Samples prepared and annealed in vacuum show signatures of mixed ferromagnetic and antiferromagnetic phases, and are insulators. The pure antiferromagnetic phase (as expected and observed in bulk materials with optimum oxygen stoichiometry) was not obtained in our experiments, even in the strongly reduced films. © 1999 American Institute of Physics.
Show PACS
71.30.+h Metal-insulator transitions and other electronic transitions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.70.Ak Magnetic properties of monolayers and thin films
73.61.At Metal and metallic alloys
72.60.+g Mixed conductivity and conductivity transitions
61.66.Bi Elemental solids
61.66.Dk Alloys
68.55.-a Thin film structure and morphology

Ferrimagnetic resonance excitation by light-wave mixing in a scanning tunneling microscope

Th. Gutjahr-Löser, W. Krieger, H. Walther, and J. Kirschner

J. Appl. Phys. 86, 6331 (1999); http://dx.doi.org/10.1063/1.371694 (4 pages) | Cited 1 time

Full Text: | Download PDF

Show Abstract
Ferrimagnetic resonance is measured in a scanning tunneling microscope. The infrared light of two lasers is focused into the tunneling junction and a difference-frequency signal in the microwave region is generated. This microwave signal is used to excite spin waves in an yttrium–iron–garnet film with a thin Au capping. The coupling of the light to the tunneling junction is explained by an antenna mechanism. Characteristic antenna patterns of the angle-dependent receiving efficiency are obtained. The mixing of the two laser frequencies is due to the nonlinearity of the tunneling junction. The microwave signal obtained is absorbed in the ferromagnetic sample if the resonance condition is fulfilled. This method might allow the measurement of magnetic properties with a lateral resolution down to the nm scale. © 1999 American Institute of Physics.
Show PACS
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Gg Ferrimagnetics
07.79.Cz Scanning tunneling microscopes
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
75.30.Ds Spin waves
07.55.-w Magnetic instruments and components
75.70.Ak Magnetic properties of monolayers and thin films
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close