PHOTOCONDUCTIVITY IN CUPROUS OXIDE SINGLE CRYSTALS

1962 ◽  
Vol 40 (12) ◽  
pp. 1703-1713 ◽  
Author(s):  
Emery Fortin ◽  
Frank L. Weichman
Keyword(s):  
Temperature Dependence ◽  
Single Crystals ◽  
Cuprous Oxide ◽  
Low Temperatures ◽  
Surface Recombination ◽  
High Resistivity ◽  
Material Surface ◽  
Conductivity Measurements ◽  
Small Temperature ◽  
Significant Difference

Measurements were made on both single and multicrystalline samples of Cu2O of high resistivity. Conductivity measurements gave three activation energies, 1.0, 0.5, and 0.027 ev, for different temperature regions. The photoconductivity at constant temperatures as a function of wavelength as well as the photoconductivity as a function of temperature at constant wavelengths were measured. Over the temperature range investigated no significant difference was found between single and multicrystalline material. Surface recombination states are postulated to explain the very small temperature dependence at low temperatures.

Anomaly of Nuclear Quadrupole Relaxation in Cu2O Prepared at Low Temperatures

1986 ◽  
Vol 41 (1-2) ◽  
pp. 382-385 ◽  
Author(s):  
J. Kasprzak ◽  
J. Lus ◽  
J. Pietrzak
Keyword(s):  
Temperature Dependence ◽  
Cuprous Oxide ◽  
Thermal Processing ◽  
Low Temperatures ◽  
Room Temperature ◽  
Quadrupole Relaxation ◽  
Temperature Dependences ◽  
Powder Samples ◽  
Nuclear Quadrupole ◽  
Nuclear Quadrupole Relaxation

The 63Cu and 65Cu NQR transitions in powder samples of cuprous oxide have been investigated from 77 to 500 K and at room temperature after annealing up to 1100 K Significant differences in T1 , NQR linewidth Δv, and their temperature dependences were found among the samples prepared in different ways. For C u20 samples obtained in low temperatures (below 380 K), the temperature dependence of T1 below 380 K is o f activation character with Ea = 0.07 eV. These results are interpreted in terms of an electron hopping mechanism. Thermal processing of these samples permits to obtain irreversible electronic state and then the spectroscopic parameters are the same as for the samples obtained in high temperatures (above 1320 K).

Structure of tetrakis(dimethylamino)ethene (TDAE) at low temperatures

1995 ◽  
Vol 210 (7) ◽  
Author(s):  
J. Bruckmann ◽  
C. Krüger ◽  
H. Borrmann ◽  
A. Simon ◽  
H. Bock
Keyword(s):  
Crystal Structure ◽  
Phase Transitions ◽  
Single Crystal ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Low Temperatures ◽  
Structure Refinement ◽  
Static Disorder ◽  
Structural Details ◽  
Different Temperatures

AbstractThe single crystal structure of TDAE was redetermined at different temperatures. Phase transitions are observed by warming the samples from low temperatures but never by cooling. Due to this special behavior it was possible to cool single crystals to 90 K. The data collected from such supercooled crystals resulted in a more precise and reliable structure refinement. Interesting structural details of the sterically overcrowded molecule are elucidated. The temperature dependence of the distortions of the nonplanar dimethylamino groups indicates dynamic behavior rather than static disorder.

Out-of-Plane and in-Plane Conduction in Insulating and Strongly Underdoped Cuprates

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3203-3206
Author(s):  
C. C. Almasan ◽  
G. A. Levin ◽  
E. Cimpoiasu ◽  
T. Stein ◽  
D. A. Gajewski ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Normal State ◽  
Low Temperatures ◽  
Elementary Step ◽  
Charge Carriers ◽  
Two Dimensional ◽  
Out Of Plane ◽  
Underdoped Cuprates

We report measurements of out-of-plane (ρ c ) and in-plane (ρab) normal-state resistivities of single crystals of insulating PrBa2Cu3O 7-δ and strongly underdoped oxygen deficient YBa2Cu3O 6.41 using a flux transformer method. In the superconducting specimens, the onset of superconductivity was suppressed by a magnetic field of 9 T. We have found that the anisotropy ρc/ρab of these samples increases monotonically at low temperatures with no signs of saturation. The temperature dependence of ρc/ρab for YBa2Cu3O6.41 is well described by ρc/ρab=a +bT-2/3, but over a smaller temperature range than for insulating PrBa2Cu3O 7-δ. Both the absence of saturation of ρc/ρab and its T-2/3 dependence indicate two-dimensional conduction. This means that the average in-plane hopping distance of the localized charge carriers increases with decreasing T according to Mott's [Formula: see text] law, while the elementary step in the c-direction remains T independent, equal to the spacing between the bilayers.

The ferromagnetic domain structure of haematite

1968 ◽  
Vol 303 (1475) ◽  
pp. 525-529 ◽  
Keyword(s):  
Low Temperature ◽  
Single Crystals ◽  
Domain Structure ◽  
Low Temperatures ◽  
Remanent Magnetization ◽  
Temperature Transition ◽  
Small Temperature ◽  
Temperature Range ◽  
Ferromagnetic Domain ◽  
Synthetic Crystals

Observations are reported of the ferromagnetic domain structure of natural and synthetic single crystals, made at temperatures close to the low temperature transition with the aid of an acetone based magnetic colloid. The domain structure of the synthetic crystals was found to change radically over a small temperature range centred around –12 °C. These changes are correlated with the measured remanent magnetization. Fairly extensive colloid patterns were found on the natural crystals at low temperatures but when the natural crystals were annealed at 1200 °C this low temperature colloid structure was no longer found.

Nachweis der verschiedenen Phasen und Phasenübergänge des Systems Fe-Ga im Konzentrationsbereich 25,7 bis 28,3 At-% Ga bei Temperaturen von 20 °C bis 720 °C mit Hilfe des Mössbauer- Effekts

1978 ◽  
Vol 33 (6) ◽  
pp. 644-650 ◽  
Author(s):  
K. Tiemann ◽  
J. Schmand
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
Phase Diagrams ◽  
Field Gradient ◽  
Temperature Interval ◽  
Low Temperatures ◽  
Small Temperature ◽  
Fe Sites ◽  
Ordering Transition ◽  
The Magnetic Field

Abstract Fe-Ga-absorbers, bcc-unordered at 20 °C, with 25.7, 27.0, and 28.3 at-% Ga were analyzed up to 720 °C with the Mössbauer effect in order to clear disagreements of former experiments of us with the then known phase diagrams. We found proofs for an ordering transition A2 -DO3 between 180 and 260 °C, a transition DO3 -Ll2 between 280 and 380 °C, a transition Ll2 -DO19 in a small temperature interval at 610 °C, and a further one DO19 - DO3 (or DO19-B2) at 630 °C. The temperature dependence of the magnetically induced Ll2-field gradient q was analyzed. Probably q is negative, while the direction of the magnetic field is parallel [1, 0, 0] in agreement with other experiments at low temperatures. Above 630 °C there seems to exist a further so far unknown ordered phase, which is probably non-cubic with at least two different Fe-sites. Our results are in considerable agreement with recently published phase diagrams, though some of our spectra allow different interpretations.

The thermal conductivity of lead at low temperatures

1958 ◽  
Vol 244 (1236) ◽  
pp. 85-100 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Plastic Deformation ◽  
Single Crystals ◽  
Superconducting State ◽  
Low Temperatures ◽  
Conductivity Measurements ◽  
Conduction Electrons ◽  
Lattice Waves ◽  
Normal States ◽  
Theory Of Superconductivity

Thermal conductivity measurements have been made upon a series of lead specimens between 1 and 4° K, in the superconducting and in the normal states. Both single crystals and polycrystals were studied, and also specimens containing various added impurities. The results in the superconducting state confirm the hypothesis that below about 1·4° K the thermal current is carried entirely by lattice waves, and that these are not scattered by conduction electrons. This conclusion is based upon three pieces of evidence: (1) the thermal conductivity K s is insensitive to the amount and species of impurity; (2) it depends upon the geometry of the specimen for sufficiently thin specimens; (3) it is sensitive to plastic deformation, which can be explained if the lattice waves are scattered by dislocations. A brief discussion is given of the possible significance of these results in the theory of superconductivity.

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