Relaxation Time Anisotropy in Cadmium Sulphide Studied with Electrical Resistivity and Magneto-Resistance Effect

1959 ◽  
Vol 14 (1) ◽  
pp. 47-56 ◽  
Author(s):  
Taizō Masumi
Keyword(s):  
Electrical Resistivity ◽  
Relaxation Time ◽  
Cadmium Sulphide ◽  
Magneto Resistance

Magneto-resistance effects in the group I metals at high fields

1957 ◽  
Vol 238 (1214) ◽  
pp. 344-357 ◽  
Keyword(s):  
Relaxation Time ◽  
Wave Vector ◽  
Hall Coefficient ◽  
Conductivity Tensor ◽  
Experimental Results ◽  
Group I ◽  
High Fields ◽  
Magneto Resistance

Measurements are reported on the resistivity and Hall coefficient of pure specimens of copper, silver and gold at 4°K in fields up to 25 kG. The theoretical form of the conductivity tensor in high fields is worked out, for arbitrary dependence of energy and relaxation time on wave-vector, and is found to be in qualitative disagreement with the experimental results. Possible causes of the discrepancy are discussed, and it is concluded that it probably arises not from quantization effects, but from the assumption in the theory that a relaxation time exists and is independent of field.

scholarly journals Coupled magnetic resonance and electrical resistivity tomography: An open-source toolbox for surface nuclear-magnetic resonance

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. F53-F64 ◽  
Author(s):  
Nico Skibbe ◽  
Raphael Rochlitz ◽  
Thomas Günther ◽  
Mike Müller-Petke
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Electrical Resistivity ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Water Content ◽  
Open Source ◽  
Electrical Resistivity Tomography ◽  
Resistivity Tomography ◽  
Wide Range ◽  
Nuclear Magnetic

Nuclear-magnetic resonance (NMR) is a powerful tool for groundwater system imaging. Ongoing developments in surface NMR, for example, multichannel devices, allow for investigations of increasingly complex subsurface structures. However, with the growing complexity of field cases, the availability of appropriate software to accomplish the in-depth data analysis becomes limited. The open-source Python toolbox coupled magnetic resonance and electrical resistivity tomography (COMET) provides the community with a software for modeling and inversion of complex surface NMR data. COMET allows the NMR parameters’ water content and relaxation time to vary in one dimension or two dimensions and accounts for arbitrary electrical resistivity distributions. It offers a wide range of classes and functions to use the software via scripts without in-depth programming knowledge. We validated COMET to existing software for a simple 1D example. We discovered the potential of COMET by a complex 2D case, showing 2D inversions using different approximations for the resistivity, including a smooth distribution from electrical resistivity tomography (ERT). The use of ERT-based resistivity results in similar water content and relaxation time images compared with using the original synthetic block resistivity. We find that complex inversion may indicate incorrect resistivity by non-Gaussian data misfits, whereas amplitude inversion shows well-fitted data, but leading to erroneous NMR models.

Electrical resistivity and magneto-resistance of very dilute Cu-Cr alloys

1975 ◽  
Vol 16 (5) ◽  
pp. 477-480 ◽  
Author(s):  
S. Legvold ◽  
T.A. Vyrostek ◽  
J.A. Schaefer ◽  
P. Burgardt ◽  
D.T. Peterson
Keyword(s):  
Electrical Resistivity ◽  
Magneto Resistance

ELECTRICAL RESISTIVITY AND MAGNETO-RESISTANCE OF La0.7Sr0.3-xAgxMnO3 PELLETS BETWEEN 10 AND 450 K

2007 ◽  
Vol 21 (05) ◽  
pp. 707-722 ◽  
Author(s):  
MANJUSHA BATTABYAL ◽  
T. K. DEY
Keyword(s):  
Electrical Resistivity ◽  
Excellent Agreement ◽  
Small Polaron ◽  
Residual Resistivity ◽  
Optical Phonon Mode ◽  
Model Based ◽  
Spin Polarized ◽  
Field Dependent ◽  
Magneto Resistance ◽  
Spin Polarized Tunneling

The temperature dependence of the electrical resistivity and magneto-resistance in silver substituted La 0.7 Sr 1-x Ag x MnO 3 pellets prepared by a simple pyrophoric method has been investigated between 10 and 450 K for H=0 and 0.8T. Ag substitution enhances the conductivity of this system. Curie temperature (T C ) also increases sharply from ~303 K (x=0.05) to ~363 K (x=0.25). Above the metal-insulator transition temperature (T MI ), the electrical resistivity is well represented by usual adiabatic polaronic transport, while in the ferromagnetic region at low temperatures, the resistivity data shows an excellent agreement to an expression containing the residual resistivity, two-magnon scattering term and the term associated with small-polaron metallic conduction, which involves a relaxation time due to a soft optical phonon mode. Based on a scenario that the doped manganites consist of phase separated ferromagnetic metallic and paramagnetic insulating regions, all the features of the temperature variation of the resistivity between ~50 K and 300 K could be described very well. All the Ag doped samples reveal resistivity minimum, which is strongly field dependent (H=0.8 T ). These minimum results have been analyzed and the observed field dependent minimum is found to be in excellent agreement to those calculated from the model based on charge carrier tunneling between antiferro-magnetically coupled grains. Field dependence of magnetoresistance at various temperatures below T c is accounted fairly well by a phenomenological model based on spin polarized tunneling at the grain boundaries. The contributions from the intrinsic part arising from DE mechanism, as well as the part originating from intergranular spin polarized tunneling are also estimated.

Magneto-resistance Effect in Cadmium Sulphide

1958 ◽  
Vol 13 (3) ◽  
pp. 314-314 ◽  
Author(s):  
Shōji Tanaka ◽  
Taizō Masumi
Keyword(s):  
Cadmium Sulphide ◽  
Magneto Resistance

The electrical resistivity of potassium below 4.2 K

1971 ◽  
Vol 325 (1561) ◽  
pp. 223-249 ◽  
Keyword(s):  
Electrical Resistivity ◽  
Relaxation Time ◽  
Point Defects ◽  
Characteristic Temperature ◽  
Band Model ◽  
Temperature Derivative ◽  
Exponential Form ◽  
Two Band Model ◽  
Umklapp Scattering ◽  
The Ideal

The electrical resistivity of potassium has been measured between 1.2 and 4.2 K for samples with various amounts of impurity, and also for samples which have been deformed and then progressively annealed. After allowing for departures for Matthiessen’s rule (M.r.) an estimate of the ‘ideal’ resistivity can be made: the logarithmic temperature derivative rises from 5.6 at 4.2 K and passes through a maximum of 9.0 at 2.1 K. The Bloch T 5 region does not extend above 1.8 K and does not contribute more than ρ = 20 x 10 -15 T 5 Ω cm to the total ideal resistivity ; at 4 K this T 5 contribution is only about 15% of the total ideal resistivity. The rest of the ideal resistivity between 1.8 and 4.2 K shows an exponential form, as expected from the freezing out of umklapp processes with a characteristic temperature of about 23 K. The measurements agree with recent calculations of Rice & Sham (1970) within about a factor of 2 over a range of 10 5 in resistivity, but they do not allow a clear choice to be made between the different forms of pseudopotential that were discussed. The deviations from M.r. for point defects in potassium appear to be accurately proportional to the ideal resistivity between 2 and 4.2 K, i.e. over a range of 300 in ideal resistivity. The magnitude of the deviations is consistent with galvanomagnetic data analysed according to the two-band model, and it implies that a small group of electrons, about 6% of the total, differs in relaxation time from the rest by a factor of about 3. However, the form of the deviations from M.r. does not seem to be compatible with the two-band model. Dislocations in potassium give a small but characteristic extra deviation from M.r. which may be correlated with umklapp scattering. No evidence was found for the momentum-non-conserving processes which have recently been suggested by Campbell, Caplin & Rizzuto (1971) to be very important in aluminium.

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