Showing papers on "Magnetoresistance published in 1971"
TL;DR: In this paper, the authors measured the resistivity, Hall coefficient, and magnetoresistance coefficient of twinned bismuth films between 1.15 and 300 K and found that the surface scattering in these films is not specular, contrary to the findings of some other workers.
Abstract: The resistivity, Hall coefficient, and magnetoresistance coefficient of well ordered but twinned bismuth films were measured between 1. 15 and 300 K. It was found that the surface scattering in these films is not specular, contrary to the findings of some other workers. At 300 K the thickness dependence of the resistivity can be roughly fitted by the Fuchs-Sondheimer boundary-scattering theory with a surface reflection coefficient of 0.6, indicating partially diffuse scattering. It was also observed that the apparent scattering becomes more diffuse with decreasing temperature until at low temperatures the data can no longer be explained by the Fuchs-Sondheimer theory. This indicates that an additional size-dependent temperature-dependent scattering mechanism exists in thin-film transport. It was observed that at low temperatures the temperature dependence of the conductivity could be explained on the basis of a constant mean free path for the thicker samples. For thinner samples, the temperature dependence of the conductivity again indicates that there is an additional scattering mechanism that becomes stronger with decreasing temperature and decreasing sample thickness. Values of the mobility and mean free path, calculated from the data, were also observed to vary consistently with the sample thickness. The conclusions, drawn from the thickness dependence of the resistivity, concerning the diffuseness of the surface scattering of the charge carriers were confirmed by the dependence of the mean free path upon the sample thickness. Finally, quantum size-effect oscillations were observed in all of the transport properties of the thin bismuth films at low temperatures. The period (about 400 \AA{}) and phase of the oscillations are in reasonable agreement with the theory and in good agreement with other values reported in the literature.
88 citations
64 citations
TL;DR: In this paper, the second derivative of the high field magnetoresistance of pure tellurium crystals at helium temperatures was measured and surface quantum states in a strong accumulation layer were discovered.
52 citations
TL;DR: In this paper, the transverse and longitudinal electrical conductivity in strong magnetic fields is calculated in the generalized Born approximation and in the self-consistentt-matrix approximation.
Abstract: To explain recent experiments on n-InSb we calculate the transverse and longitudinal electrical conductivity in strong magnetic fields. We consider a free electron-point impurity system in the generalized Born approximation, and in the self-consistentt-matrix approximation. The position, shape and amplitude of the Shubnikovde Haas oscillations and the quantum limit behaviour are in good agreement with experiment.
48 citations
TL;DR: In this paper, the magnetoresistance, Hall effect, thermopower, thermal resistivity, and Nernst-Ettings-hausen effects are measured in magnetic fields to 10.3 T (103 kG) and at temperatures between 1.1 and 4.2 K. The major results are that majority-carrier electrons and holes are assigned to specific locations in the Brillouin zone; the electrons assigned to be around the center of the zone edge (point $K$).
Abstract: The magnetoresistance, Hall effect, thermopower, thermal resistivity, and Nernst-Ettings-hausen effects are measured in magnetic fields to 10.3 T (103 kG) and at temperatures between 1.1 and 4.2 K. Samples are highly ordered pressure-annealed pyrolytic graphite. The major results are that majority-carrier electrons and holes are assigned to specific locations in the Brillouin zone; the electrons are assigned to be around the center of the zone edge (point $K$). The first observation of spin-split Landau levels is made. A study of distorted line shapes of thermopower quantum oscillations shows agreement with a theory by Horton. Sugihara and Ono's theory, predicting field values for Landau level crossings of the Fermi energy in graphite, is confirmed for fields below 4 T.
47 citations
TL;DR: In this article, the effect of static magnetic fields up to 210 kG on the characteristics of commercial germanium and platinum resistance thermometers was measured at various temperatures in the range 3.5-78 K.
Abstract: The effect of static magnetic fields up to 210 kG on the characteristics of commercial germanium and platinum resistance thermometers was measured at various temperatures in the range 3.5–78 K. Measurements of the transverse (sample current I normal to magnetic field H) and longitudinal (I∥H) magnetoresistance were carried out on both types of thermometers. A description is given of the dc resistance measuring technique used in these experiments. This method is a semiautomatic potentiometric scheme which increases the speed of measurement while maintaining high resolution and reasonable accuracy. The magnetoresistance of the germanium sensors was found to be large and orientation dependent over the temperature range investigated. These effects preclude the use of germanium elements, as presently fabricated, for temperature sensors in a high magnetic field environment. In the case of platinum resistance thermometers, the magnetoresistance at temperatures above 30 K is small enough so that it becomes practi...
45 citations
TL;DR: In this article, an approximate solution for the complex propagation constant in semiconductor loaded waveguides is obtained by expansion of the fields in terms of a finite number of the empty waveguide modes.
Abstract: Approximate solutions for the complex propagation constant in semiconductor loaded waveguides are obtained by expansion of the fields in terms of a finite number of the empty waveguide modes. Solutions are obtained for the case of partial loading in the narrow dimension of the guide, which explicitly exhibit the non-reciprocal effects observed in the presence of a transverse magnetic field. Coupling between the TE/sub 10/ and TM/sub 11/ empty waveguide modes is shown to explain qualitatively the observed experimental effects. Good quantitative agreement with experiments using Si samples is obtained.
37 citations
TL;DR: In this article, a study of the temperature, magnetic field, and doping dependence of the conductivity, Hall coefficient, and magnetoresistance of gray tin has been interpreted within the framework of the Groves-Paul band structure model allowing the determination of several of its parameters as well as an investigation of the charge carrier scattering mechanisms.
34 citations
TL;DR: In this paper, the Hall mobility, thermoelectric power, magnetoresistance and optical absorption coefficient of MgxPb1−x Te alloys with 0less-than-or-eq, slantx less-thanor-equivalent, and slant006 have been measured at temperatures within the range 77 to 450 K.
Abstract: The Hall mobility, thermoelectric power, magnetoresistance and optical absorption coefficient of MgxPb1−x Te alloys with 0less-than-or-eq, slantxless-than-or-eq, slant006 have been measured at temperatures within the range 77 to 450 K. It has been found that alloying PbTe with MgTe increases the direct energy gap and the resulting transport properties are similar to those of CdxPb1−x Te alloys.
32 citations
TL;DR: Magnetoresistance and magnetization measurements on the granular Ni-SiO 2 system show the existence of a ferromagnetic to supermagnetic transition as mentioned in this paper, and it is concluded that the intergrain tunneling probability depends on the orientation of the electronic spin.
29 citations
TL;DR: In this article, the influence of the high field/low field transition upon the interpretation of the transverse magnetoresistance and the Hall effect in dilute polycrystalline alloys containing a magnetic solute is considered.
TL;DR: In this paper, the temperature dependence of the electrical resistivity of cubic ferromagnetic U3P4 and U3As4 single crystals along [100], [110], and [111] in the temperature range 2 to 320 °K.
Abstract: An investigation is made of the temperature dependence of the electrical resistivity of cubic ferromagnetic U3P4 and U3As4 single crystals along [100], [110], and [111] in the temperature range 2 to 320 °K. The magnetoresistivity has been examined from 80 °K to the Curie temperature in magnetic fields up to 5.3 kOe. It is found that the compounds show anisotropic behaviour, a convex Q vs. T dependence which is unusual for a simple collinear ferromagnet, and a large magnetoresistivity (ΔR/R = 10 to 30%). The measurements of the thermal expansion of polycrystalline samples show that in U3P4 strong exchange striction occurs.
[Russian Text Ignored].
TL;DR: In this article, a theory on the galvanomagnetic effect of two-dimensional electron gas in silicon surface inversion layers is presented together with experimental results on the (111) surface of silicon.
Abstract: In this paper a theory on the galvanomagnetic effect of two-dimensional electron gas in silicon surface inversion layers is presented together with experimental results on the (111) surface of silicon. The calculation takes into account two-dimensional many-valley energy band structure and energy-dependent relaxation time. An expression for the ratio of Hall mobility to conductivity mobility is obtained and the ratio is found to depend on crystal orientations, scattering mechanisms and carrier concentrations. The theory of magnetoresistance is compared with experimental results measured on the (111) surface of silicon at 300°K and 77°K. Validity of the two-dimensional electron gas model for electrons in silicon surface inversion layers is evaluated and it is found that electrons behave neither as two-dimensional nor as three-dimensional gas but as the mixture of them at room temperature.
TL;DR: In this paper, the magnetic properties and electrical properties (the electrical resistivity, the Hall effect and the magnetoresistance effect) were measured on hot pressed polycrystalline samples of Hg 1-x Ag x Cr 2 Se 4 (0≤ x ≤ 0.0155) and Hg 2- y In y Cr 2 SE 4 ( 0≤ y ≤ 0.02).
Abstract: Measurements of the magnetic properties and the electrical properties (the electrical resistivity, the Hall effect and the magnetoresistance effect) were performed on hot pressed polycrystalline samples of Hg 1- x Ag x Cr 2 Se 4 (0≤ x ≤0.0155) and of Hg 1- y In y Cr 2 Se 4 (0≤ y ≤0.02). It was found that the Curie temperature of Hg 1- x Ag x Cr 2 Se 4 increased as the amount of the Ag dopant increased, whereas the Curie temperature of Hg 1- y In y Cr 2 Se 4 decreased with increasing concentration of the In dopant. The In-doped HgCr 2 Se 4 showed a high resistivity, a large Hall effect, and a large negative magnetoresistance effect; the Ag-doped HgCr 2 Se 4 showed a low resistivity, a small Hall effect and a small critical scattering of positive magnetoresistance. The different effects of the dopants. Ag and In, on the properties of HgCr 2 Se 4 which were studied is satisfactorily explained by the change in carrier concentration produced by the dopants.
TL;DR: In this paper, a theoretical model and experimental data on chromium and tungsten are presented which show that poor lead geometry combined with a highly anisotropic magnetoconductivity can produce a zero resistance when the magnetic field is parallel to the current.
Abstract: A theoretical model and experimental data on chromium and tungsten are presented which show that poor lead geometry combined with a highly anisotropic magnetoconductivity can produce a ``zero resistance'' when the magnetic field is parallel to the current.
Patent•
IBM1
TL;DR: A MAGNETORESISTIVE SENSING DEVICE for detecting MAGNETIC FLUX has been proposed in this paper, in which the MAGNETIZATION VECTOR will return to its REST state when the noisy sensor is removed.
Abstract: A MAGNETORESISTIVE SENSING DEVICE FOR DETECTION OF MAGNETIC FLUX, COMPRISING A MAGNETORESISTIVE SENSING ELEMENT IN WHICH THE SHAPE ANISOTROPY FIELD IS SUBSTANTIALLY PERPENDICULAR TO THE UNIAXIAL ANISOTROPY FIELD THE LARGER OF THESE TOW MAGNETIC FIELDS IS IN A DIRECTION WHICH IS SUBSTANTIALLY NORMAL TO THE DIRECTION OF THE SIGNAL FLUX WHICH IS TO BE DETECTED, TO INSURE THAT THE MAGNETIZATION VECTOR OF THE SENSING ELEMENT WILL RETURN TO ITS REST STATE WHEN THE SIGNAL MAGNETIC FLUX IS REMOVED THE EASY AXIS OF THE SENSING ELEMENT CAN BE EITHER PARALLEL OR NORMAL TO THE SIGNAL MAGNETIC FIELD DIRECTION CURRENT THROUGH THE SENSING ELEMTN IS PREFERABLY PROVIDED BY A CONSTANT CURRENT SOURCE CONNECTED TO THE ELEMENT THE DIRECTION OF CURRENT THROUGH THE ELEMENT CAN BE EITHER ALONG THE DIRECTION OF THE QUIESCENT MAGNETIZATION STATE OR PERPENDICULAR TO IT APPLICATIONS INCLUDE MAGNETIC BUBBLE DOMAIN SENSING AND SENSING OF STORED MAGNETIC SIGNALS ON DISKS OR TAPES
TL;DR: In this paper, the changes in magnetoresistance resulting from substitutional introduction of boron atoms into the lattice of a single crystal of graphite were studied, as well as in polycrystalline graphite when defects (vacancies, interstitial atoms, etc.) are introduced by neutron irradiation.
TL;DR: In this paper, a simple ellipsoidal energy band is proposed for the former, and an n -germanium type band structure is proposed to solve the magnetoresistance problem.
Abstract: N -type Cd 3 As 2 single crystals are prepared by a modified sublimation method, and their galvanomagnetic properties are measured above 2 K. The Hall coefficient is constant from 2 to 300 K, and no anisotropy is observed. The Hall mobility is constant below 15 K and then decreases gradually with increasing temperature. Conduction carriers are degenerate and scattered by both ionized impurities and the acoustical lattice vibration below 300 K. The resistance increment ( Δ ρ/ρ 0 ) 001 010 due to the magnetoresistance effect approaches 14 at 23,000 gauss, and not yet saturates. The longitudinal magnetoresistance coefficient M 001 001 is nearly equal to zero in samples with carriers of 3×10 18 /cm 3 and does not vanish in samples with carriers of 1×10 18 /cm 3 . A simple ellipsoidal energy band is proposed for the former, and an n -germanium type band structure is proposed for the latter. The longitudinal magnetoresistance is not zero for samples with carriers of 1×10 19 /cm 3 .
TL;DR: In this article, the thermal emf and magnetoresistance of liquid selenium were measured with graphite electrodes in a pressure vessel up to 1300K and a sign change of the thermoelectric power was observed at about 990K.
Abstract: The thermal emf and the magnetoresistance of liquid selenium were measured with graphite electrodes in a pressure vessel up to 1300K. A sign change of the thermoelectric power was observed at about 990K. Above this temperature selenium is an n-type semiconductor. A relatively high magnetoresistance was measured above 990K. Experiments for measuring the Hall effect with graphite electrodes up to 870K failed. Considering the results of the experiments a model for the conduction mechanism could be suggested.
TL;DR: In this article, the dependence of magnetoresistance on magnetic field was investigated at 77°K for soft carbons prepared from Texas petroleum coke (no-binder) by heat treatments in the range 1400°-3000°C.
Abstract: The dependence of magnetoresistance on magnetic field is investigated at 77°K for soft carbons prepared from Texas petroleum coke (no-binder) by heat treatments in the range 1400°–3000°C. For specimens heat treated at temperatures between 1400° and 2200°C, the magnetoresistance is negative; its absolute value increases monotonically with increasing heat treatment temperature (HTT) and with increasing magnetic field. For specimens heat treated between 2400° and 2450°C, the magnetoresistance is negative and tends to saturate at higher fields. The absolute value becomes larger for lower HTT. Specimens heat treated between 2400° and 2450°C show a magnetoresistance which is negative at low fields, passes through minimum and becomes greater for lower HTT. For specimens with HTT≥2570°C, no negative magnetoresistance is observed even at low fields. Some discussion of the effects found is included.
TL;DR: In this article, a nonmagnetic high pressure cell capable of being used for a variety of magnetic measurements to over 100 kilobars is described, which is suitable for both pulsed and wide line nuclear magnetic resonance (NMR) measurements.
Abstract: A nonmagnetic high pressure cell capable of being used for a variety of magnetic measurements to over 100 kilobars is described. A Bridgman anvil type of cell, it has a 3–5 mm3 sample volume and is suitable for both pulsed and wide line nuclear magnetic resonance (NMR) measurements. In addition to a detailed description of the apparatus used for wide line NMR measurements, the use of the high pressure cell for magnetoresistance and susceptibility measurements is described.
TL;DR: In this article, the four anisotropy constants of the orientational magnetoresistance of Gd single crystals in a range from 77 K to 400 K have been determined.
Abstract: Measurements of orientational and forced magnetoresistances have been done on Gd single crystals in a range from 77 K to 400 K. According to a phenomenological analysis, the four anisotropy constants of the orientational magnetoresistance were determined. The temperature dependence of the orientational magnetoresistance showed generally two minima and a maximum, While the constants showed single minimum. This appears to be attributable partly to the variation of the easy direction with temperature. The temperature dependence of the forced magnetoresistance also was anisotropic. This seems to be related to the variation of the electrical resistance with temperature.
TL;DR: The geometrical magnetoresistance scattering factor has been measured for vapour-phase epitaxial GaAs in the temperature range 77 to 400 K as discussed by the authors, which is in fair agreement with theoretical expectations.
Abstract: The geometrical magnetoresistance scattering factor has been measured for vapour-phase epitaxial GaAs in the temperature range 77 to 400 K. These measurements eliminate experimental difficulties associated with other determinations. The factor is approximately unity throughout the temperature range and is 0·96±0·08 at 300 K, which is in fair agreement with theoretical expectations.
TL;DR: In this article, it was shown that the linear increase of the High field magnetoresistance in Al depends boths on the type of defect structure and on the crystal orientation, and the results of such measurements show clearly that linear increase in the magnetoreduction rate depends both on the defect type and crystal orientation.
TL;DR: The low-field magnetoresistance of single crystals of some dilute copper-and silver-based alloys has been measured at 1.5 K and 4.2 K as mentioned in this paper.
Abstract: The low-field magnetoresistance of single crystals of some dilute copper-and silver-based alloys has been measured at 1.5 K and 4.2 K. The alloys studied were CuAu and AgAu (homovalent impurity): CuZn and CuGe (heterovalent impurity); and CuNi and AgPd (transition metal impurity). The results, in conjunction with previously measured Hall coefficients, were interpreted under the assumption that an anisotropic relaxation time can be defined which has a different anisotropy for each impurity. By describing the anisotropy in terms of `relaxation time models' a possible variation in the relaxation time over the Fermi surface has been deduced for the CuAu, AgAu, CuNi and AgPd alloys, but the magnetoresistance of the CuZn and CuGe alloys cannot be interpreted in terms of the models described here.
01 Jan 1971
TL;DR: In the presence of magnetic fields the use of resistance thermometry is seriously limited by the magnetoresistance (Hall) effect [1] as mentioned in this paper, which is also known as the Hall effect.
Abstract: Cryogenic thermometry below about 20°K is complicated by several factors such as self-heating, mathematical representability, reduced sensitivity, etc., and in the presence of magnetic fields the use of resistance thermometry is seriously limited by the magnetoresistance (Hall) effect [1].