Showing papers on "Magnetoresistance published in 1985"
IBM1
TL;DR: A simulation of the magnetoresistance of very small wires shows sample-specific, aperiodic structure due to the non-self-averaging nature of quasi-one-dimensional conductors in this size range as discussed by the authors.
Abstract: A simulation of the magnetoresistance of very small wires shows sample-specific, aperiodic structure due to the non-self-averaging nature of quasi-one-dimensional conductors in this size range. This explains earlier failures to observe flux-periodic magnetoresistance in very small rings. Analysis of the temperature and size dependence of the effect gives good agreement with experiment. A prediction is made for the experimental conditions in which oscillations periodic with flux $\frac{\mathrm{hc}}{e}$ will be observed.
223 citations
TL;DR: In the MR magnetic head of the present invention, its sensing element (2) comprises a plurality of superposed magnetic layers (4,5) having magnetoresistance effect in at least one of them and a nonmagnetic intermediate layer (3) sandwiched therebetween, and a sensing current is fed to flow in the sensing element in the same direction as a signal magnetic field applied to the element as discussed by the authors.
Abstract: In the MR magnetic head of the present invention, its sensing element (2) comprises a plurality of superposed magnetic layers (4,5) having magnetoresistance effect in at least one of them and a nonmagnetic intermediate layer (3) sandwiched therebetween, and a sensing current (i) is fed to flow in the sensing element (2) in the same direction as a signal magnetic field applied to the element. Each of the magnetic layers (4,5) is so formed as to have an easy axis of magnetization substantially perpendicular to the signal magnetic field or to have an isotropic magnetic characteristic in the magneticfilm plane, thereby avoiding generation of Barkhausen noise with certainty.
154 citations
TL;DR: Observation d'oscillations aperiodiques de la magnetoconductivite de couches d'inversion etroites dans le silicium-p inclus dans un dispositif MOSFET.
Abstract: Aperiodic oscillations are observed in the magnetoresistance of narrow inversion layers in p-type Si. The dependence of the oscillations on Fermi energy indicates that they are not the result of a shift with magnetic field of the energies of electronic states but rather arise from a change in the phase of the wave functions.
97 citations
TL;DR: In this paper, the authors measured the electrical resistivity, magnetoresistance, magnetic susceptibility and magnetization of CeCu 6 in the temperature region of 0.6 K to room temperature.
Abstract: We have measured the electrical resistivity, magnetoresistance, magnetic susceptibility and magnetization of CeCu 6 in the temperature region of 0.6 K to room temperature. The magnetic property is extremely anisotropic, reflecting the orthorhombic crystal structure. The anisotropy of negative magnetoresistance can be qualitatively understood by the corresponding magnetization. We have found that CeCu 6 is a typical Kondo lattice substance, having no magnetic ordering. The Kondo temperature is estimated as 2–3 K.
85 citations
IBM1
TL;DR: In this article, the Campbell-Fert-Jaoul theory for anisotropic magnetoresistance is extended and a new formula derived for amorphous metalloid-containing alloys, as well as for weak ferromagnets.
Abstract: The Campbell-Fert-Jaoul theory for anisotropic magnetoresistance is extended and a new formula derived for amorphous metalloid-containing alloys, as well as for weak ferromagnets. It accounts semiquantitatively for experimental data on amorphous Fe-B, Fe-Ni-B, and Fe-Ni-P-B, and also on concentrated polycrystalline Fe-Ni.
77 citations
TL;DR: Anisotropic magnetization with extremely sharp oscillatory structure similar to that expected for a quantized two-dimensional electron gas is found, and the temperature and field dependences of the anomalies suggest a series of first-order phase transitions as opposed to the conventional de Haas-van Alphen effect.
Abstract: We have utilized a novel technique to measure both the magnetization and magnetoresistance of a single crystal of ${(\mathrm{TMTSF})}_{2}$Cl${\mathrm{O}}_{4}$ in the regime where the magnetic field induces a series of metal-to-semimetal transitions. We find anisotropic magnetization with extremely sharp oscillatory structure similar to that expected for a quantized two-dimensional electron gas. However, the temperature and field dependences of the anomalies suggest a series of first-order phase transitions as opposed to the conventional de Haas-van Alphen effect. The entropy loss is comparable to the entropy of the electron gas.
76 citations
TL;DR: In this paper, the authors measured the electrical resistivity, Hall coefficient, magnetoresistance, magnetic susceptibility and magnetization of a dense Kondo substance Ce x La 1- x Cu 6 (x = 0-1).
Abstract: We have measured the electrical resistivity, Hall coefficient, magnetoresistance, magnetic susceptibility and magnetization of a dense Kondo substance Ce x La 1- x Cu 6 ( x =0-1). The dilute Kondo impurity state is found to be retained below x =0.1-0.2 in Ce x La 1- x Cu 6 , having a constant value of the unitarity limit in the magnetic resistivity. On the other hand, the Kondo lattice is formed above x =0.8-0.9 because the magnetic resistivity decreases with the decrease of the temperature and the temperature dependence of negative magnetoresistance shows a minimum around 1 K.
66 citations
TL;DR: In this paper, it was shown that the Hall voltage is hole-like, its variation versus magnetic field is linear up to 33 kOe, and peaks in magnetoresistance are observed above a threshold field of 41kOe.
Abstract: At 0.1 K, in the normal state, the Hall voltage is hole like, its variation versus magnetic field is linear up to 33 kOe. The measured Hall constant, 4xl0−9 m 3/As, does not vary between 0.1 and 7 K. In a magnetic field higher than 33 kOe, at low temperature, the magneto transport properties are very dependent on the cooling rate, even when a very low concentration of defects is expected. In standard conditions (4 hours from 30 to 4.2 K) electron like quantized Hall voltage and peaks in magnetoresistance are observed above a threshold field of 41 kOe. At the lowest cooling rate (70 hours from 30 to 4.2 K) strong hole like dips appear in the Hall voltage and the threshold field is 33 kOe. These results are understood within a model associating spin density wave phases and fully occupied Landau levels.
65 citations
Patent•
25 Apr 1985TL;DR: A magnetoresistive sensor used for emitting of electric signals in dependency on the position or the speed of a ferromagnetic body includes magnetorsistive measuring strips (10) on a substrate (12) which are exposed to a stationary magnetic field (H) such that a large field component (Hy) extends perpendicular to the measuring strips and a substantially smaller field component(Hx) in the plane of the measuring strip and at an angle of about 45° to the direction of a measuring current flowing through the sensors as discussed by the authors.
Abstract: A magnetoresistive sensor used for emitting of electric signals in dependency on the position or the speed of a ferromagnetic body includes magnetoresistive measuring strips (10) on a substrate (12) which are exposed to a stationary magnetic field (H) such that a large field component (Hy) extends perpendicular to the measuring strips and a substantially smaller field component (Hx) in the plane of the measuring strips and at an angle of about 45° to the direction of a measuring current flowing through the measuring strips. By approaching a ferromagnetic body (14) to the stationary field (H) additional field components (Hz and Ht) start acting on the measuring strips. The magnetic field component Ht generated in the plane of the measuring strips changes in dependency on the position or speed of the ferromagnetic body and affects measuring current accordingly.
59 citations
TL;DR: The results agree with Larkin's theory in its range of validity but differ from tentative extensions of his theory to higher magnetic fields which have appeared in the literature.
Abstract: We address the problem of the magnetoresistance of a disordered two-dimensional superconductor in the fluctuation regime above T/sub c/. We extend the Maki-Thompson result to temperatures closer to T/sub c/ and to higher magnetic fields by considering the magnetic field dependence of the superconducting fluctuations. We also obtain the zero-field conductivity at all temperatures above T/sub c/. Our results agree with Larkin's theory in its range of validity but differ from tentative extensions of his theory to higher magnetic fields which have appeared in the literature.
51 citations
TL;DR: An abrupt rise in the Hall resistance and magnetoresistance at a characteristic field H_c which is a significant function of temperature is observed which allows us to reject magnetic freezeout or localization by disorder as possible mechanisms.
Abstract: We have performed magnetoresistance and Hall-resistance measurements on low-carrier-concentration n-type samples of Hg_(0.76)Cd_(0.24)Te at millikelvin temperatures. We observe an abrupt rise in the Hall resistance and magnetoresistance at a characteristic field H_c which is a significant function of temperature and which allows us to reject magnetic freezeout or localization by disorder as possible mechanisms. We believe our data provide compelling evidence for a model where the magnetic field induces localization of the electrons into a three-dimensional Wigner lattice.
TL;DR: In this paper, the electrical resistivity, specific heat, magnetoresistance, magnetic susceptibility and magnetization of a single crystal in the temperature region of 14 K to room temperature were measured.
Abstract: We have measured the electrical resistivity, specific heat, magnetoresistance, magnetic susceptibility and magnetization of CeCu 2 single crystal in the temperature region of 14 K to room temperature CeCu 2 is found to be a so-called dense Kondo substance with a large specific heat coefficient of 180 mJ/mole·K 2 around 10 K The magnetic susceptibility and the negative magnetoresistance are extremely anisotropic, reflecting the orthorhombic crystal structure The antiferromagnetic ordering is suggested below 30 K
TL;DR: In this paper, a magnetic transducer using a magnetoresistance effect is described, consisting of a hard magnetic film and a conductive film through which current for applying the transverse biasing magnetic field to the magnetoresistive film flows.
Abstract: Disclosed is a magnetic transducer using a magnetoresistance effect, comprising a magnetoresistive film, a hard magnetic film for applying a transverse biasing magnetic field thereto, and a conductive film through which current for applying the transverse biasing magnetic field to the magnetoresistive film flows. The conductive film may be either in electrical contact with or in electrical insulation from the magnetoresistive film. In this magnetic transducer, even when the heights of the respective constituents have changed, the transverse biasing magnetic field to be applied does not change considerably, and an optimum bias field strength is readily attained.
TL;DR: In this paper, a detailed critical analysis is made of a large number of experimental papers dealing with studies of the conductivity, Hall effect, and magnetoresistance in HgCdTe crystals as a function of temperature, pressure, and magnetic field.
Abstract: Specific features of transport phenomena in gapless semiconductors which are due to both peculiarities of the electron spectrum of an ideal crystal and those of the impurity states in these semiconductors, are discussed. A detailed critical analysis is made of a large number of experimental papers dealing with studies of the conductivity, Hall effect, and magnetoresistance in HgCdTe crystals as a function of temperature, pressure, and magnetic field. On the strength of this analysis it is concluded that the perturbing action of the potential of acceptor-type impurities leads to effective overlap of the valence band with the conduction band. As a result, when the impurity concentration is sufficiently high, and exceeds that at which the Mott-Anderson transition occurs, the density of states of a p-type zero-gap semiconductor differs substantially from that of an ideal crystal, and is similar to that of a semimetal.
TL;DR: In this paper, the effects of the starting material Ce and the crucible on the Kondo lattice formation of CeCu 6 have been studied through the measurements of the electrical resistivity, thermoelectric power, negative magnetoresistance and magnetic susceptibility.
Abstract: Impurity effects of the starting material Ce and the crucible on the Kondo lattice formation of CeCu 6 have been studied through the measurements of the electrical resistivity, thermoelectric power, negative magnetoresistance and magnetic susceptibility.
TL;DR: In this paper, the specific heat of a single crystalline CeCu6 was measured at low temperatures down to 0.15 K in magnetic fields up to 6 T. The magnetic fields suppressed C/T at low temperature, indicating the heavy Fermi-liquid nature of a ground state.
TL;DR: In this article, the theoretical calculations of Alt'shuler et al. and Lee and Ramakrishnan for the contributions to magnetoresistance from weak localization and electron-electron interactions in a disordered system are given.
Abstract: We start from the theoretical calculations of Alt'shuler et al. and Lee and Ramakrishnan for the contributions to magnetoresistance from weak localization and electron-electron interactions in a disordered system. We give analytic expressions which can be more easily handled by experimentalists. Our results on the amorphous alloys La 3 Al and La 3 Ga are presented and interpreted using these equations to get the best fit A partir des calculs theoriques d'Alt'shuler et de Lee et Ramakrishnan dans un systeme desordonne on obtient des formes analytiques d'utilisation facile
TL;DR: In this paper, the theory for obtaining mobility and carrier concentration profiles by the Hall effect, magnetoresistance, and capacitance-conductance methods is developed in the relaxation time approximation.
Abstract: The theory for obtaining mobility and carrier concentration profiles by the Hall‐effect, magnetoresistance, and capacitance‐conductance methods is developed in the relaxation‐time approximation. This theory is then applied to semiconductors in which a Schottky barrier is used to control a depletion region. Particular emphasis is given to field‐effect transistor structures which are ideally suited for geometric magnetoresistance measurements. A unique feature of the present model is the correction for finite gate (Schottky‐barrier) current, which can be very important under forward‐gate‐bias conditions. The ability to use forward‐bias makes the near‐surface region more accessible. Also, parasitic resistance effects are treated. We apply these results to GaAs conducting layers formed by direct implantation of 4×1012/cm2, 100‐keV Si ions into Cr‐doped GaAs.
TL;DR: In this article, the normal phase of UPt3 is characterized by a high thermal conductivity with a strong T2 term, by a coherence length smaller than the mean free path, and by lower and upper critical fields H(0)c1∼60 Oe and Hc2( 0)∼26 kOe.
Abstract: Experiments on the normal phase of UPt3 show a large positive magnetoresistivity, almost temperature‐independent, linear in field, and a positive thermoelectric power which is not linear in temperature as T→0. The superconducting phase is characterized by a high thermal conductivity with a strong T2 term, by a coherence length smaller than the mean free path, and by lower and upper critical fields H(0)c1∼60 Oe and Hc2(0)∼26 kOe.
TL;DR: In this article, a review of recent studies of electrical transport in thin suicide films is presented, where resistivity as a function of temperature, Hall effect, and magnetoresistance have been characterized for CoSi2 and NiSi2.
Abstract: This paper reviews our recent studies of electrical transport in thin suicide films. Resistivity as a function of temperature, Hall effect, and magnetoresistance have been characterized for CoSi2 and NiSi2 and in conjunction with band theory provide estimates of important electronic parameters, viz. carrier densities and carrier scattering lengths. Resistivity data for TiSi2 and TaSi2 are included. Also examined in resistivity are (i) effects produced by ion bombardment which show CoSi2 to have an unusual susceptibility to radiation damage and (ii) classical size effects in the very thin film regime which show the boundary scattering to be principally specular. As an application we describe a Si/CoSi2/Si heterostructure transistor recently developed.
TL;DR: In this article, a single phase hexagonal disilicide was found in polycrystalline TaSi2 thin films, which were prepared by furnace reaction of ion beam sputtered tantalum layers with silicon surfaces.
Abstract: Polycrystalline TaSi2 thin films were prepared by furnace reaction of ion beam sputtered tantalum layers with silicon surfaces. X‐ray diffraction measurements indicate that the films are single phase hexagonal disilicide. Impurity levels are at or below the detection limits of Auger spectroscopy. The samples exhibit a room temperature intrinsic resistivity of ∼40 μΩ cm and a residual resistivity component as low as 4 μΩ cm. The Hall coefficient is negative, giving an apparent electron concentration of 6.5×1022 cm−3 at room temperature. A representative carrier mobility of 58 cm2/V s at room temperature (obtained from geometrical magnetoresistance measurements) was much larger than the Hall mobility (1.9 cm2/V s), suggesting multicarrier effects. The galvanomagnetic properties can be described by the equations for two degenerate, isotropic bands and be given a physical interpretation similar to that of Mott’s s‐d scattering model. However, it is emphasized that the two‐band model is likely only a crude app...
TL;DR: Oscillations of the resistance, corresponding to an integer number of flux quanta ${\ensuremath{\varphi}}_{0}$=hc/2e per unit loop are reported.
Abstract: We have measured the magnetoresistance of two-dimensional arrays of nonsuperconducting metallic rings made of gold and copper wires, in low magnetic field between 60 mK and 9 K. For the first time, oscillations of the resistance, corresponding to an integer number of flux quanta ${\ensuremath{\varphi}}_{0}$=hc/2e per unit loop are reported. The observed anomalous behavior of the low-temperature resistance of Au samples is attributed to Kondo impurities.
TL;DR: In this article, a method for measuring the electron mobility, velocity, and sheet carrier concentration in modulation-doped structures as functions of electric field through the use of the geometrical magnetoresistance effect is described.
Abstract: We describe a method for measuring the electron mobility, velocity, and sheet carrier concentration in modulation-doped structures as functions of electric field through the use of the geometrical magnetoresistance effect. Because the geometry of the structures is identical to that of ungated FET's, these measurements are well suited for studying the electron velocity in MODFET's. We see that the mobility quickly decreases from its low field value with increasing electric field and observe significant electron injection from the contacts. The electron velocity increases to about 1.4 × 107cm/s at 3000 V/cm at 77 K before domain formation prevents accurate measurements at higher fields.
TL;DR: In this article, the magnetic properties of a magnetoresistive thin-film sensor biased using a permanent magnet thin film were investigated and the output of the sensor was very high.
Abstract: Magnetic characteristics have been investigated for a magnetoresistive thin‐film sensor biased using a permanent magnet thin film. Here, Co‐Pt thin film is applied to the device as a bias film. Such microlithographed Co‐Pt thin films show the same magnetic properties as as‐sputtered films. Biasing strength depends on the permanent magnet film thickness, its composition or magnetic properties, and the biasing angle. The output of the sensor is very high.
TL;DR: Magnetic susceptibility and magnetoresistance of CeB 6 have been measured in magnetic fields H 6 and SmB 6 lattice parameters at pressures p⩽100 kbar as discussed by the authors.
TL;DR: In this paper, the temperature dependence of negative magnetoresistance, angular dependence of superconducting critical field and the anisotropic magnetic susceptibility in CeCu 2 Si 2 have been experimentally obtained and discussed on the basis of the tetragonal crystalline field.
TL;DR: In this paper, a model of transverse magnetoresistance (MR) in metal due to sample-thickness variations is presented, which is applied to magnetoreduction data on well annealed, polycrystalline aluminum plates which are wedge shaped, or which contain surface defects such as steps, grooves, or projections.
Abstract: A model of transverse magnetoresistance (MR) in metals due to sample-thickness variations is presented. It predicts larger magnetoresistance then do previous models. The model is applied to magnetoresistance data on well annealed, polycrystalline aluminum plates which are wedge shaped, or which contain surface defects such as steps, grooves, or projections. For wedge-shaped samples or samples containing a surface step, the model predicts magnetically induced voltages which differ on opposite sides of the sample, and which are not strictly linear in magnetic field strength B. Both phenomena occur with the predicted magnitudes. For grooves or projections which extend completely across the width of the sample, the model predicts a MR which is linear in B (LMR) and directly proportional to both the groove (projection) depth (height) and the sample width. The data are found to be in quantitative agreement with prediction. The prediction and observation of a very large LMR for large surface defects provides at least a partial resolution of a disagreement in the literature concerning the magnitude of LMR in single-crystal Al samples when B is directed along the [110] crystallographic axis. Thermal magnetoresistance measurements are shown to be consistent with the electrical measurements. Measurements are also reported on (i) the angular variation of MR when B is rotated away from the perpendicular to the sample surface; (ii) MR for surface defects which extend only part way across the sample; and (iii) MR for surface defects in unannealed Al plates.
TL;DR: In this article, the authors measured the resistance versus temperature (RT) characteristics and magnetoresistance (MR) of 1/8 W nominal 68 Ω and 100 Ω Matsushita carbon resistors of grade ERC-18SG at temperatures between 8 and 0.05 K, in magnetic fields up to 84kOe (84 × 106/4 π Am−1).
TL;DR: It is shown that the results of Hikami et al. are universally valid for electrons with an arbitrarily complex Fermi surface (anisotropic, several bands) and arbitrary impurity scattering (an isotropic, interband scattering) and the complex band-structure and scattering properties enter only in the resistivity, the electronic density of states, and properly averaged lifetimes.
Abstract: Weak-localization effects, especially the dependence of the resistance on a magnetic field, have become a unique probe for determining characteristic times for conduction electrons in metals. Analysis of the magnetoresistance data is usually made with the theory of Hikami et al., which is derived in the model of free electrons and s-type impurity scattering. We show that the results of Hikami et al. are universally valid for electrons with an arbitrarily complex Fermi surface (anisotropic, several bands) and arbitrary impurity scattering (anisotropic, interband scattering). The complex band-structure and scattering properties enter only in the resistivity, the electronic density of states, and properly averaged lifetimes, which can be obtained from a magnetoresistance experiment.
TL;DR: In this article, conductivity measurements made on special GaAs metal semiconductor field effect transistors (MESFETs), doped slightly in excess of the Mott critical doping level, so that localization and interaction effects are important in governing the electronic transport properties are presented.
Abstract: This paper presents conductivity measurements made on special GaAs metal semiconductor field effect transistors (MESFETs), doped slightly in excess of the Mott critical doping level, so that localization and interaction effects are important in governing the electronic transport properties. The measurements were made as a function of temperature (down to the dilution refrigerator range) and in transverse and parallel magnetic fields. The dimensionality of the processes has been ascertained and is compared with the relative sizes of the channel thickness, localization length, interaction length and with the sub-band energy separation. The inelastic length, L in, has been measured by two independent methods, using perpendicular and parallel magnetoresistance, which give self-consistent results. To a first approximation, effects were found to be two-dimensional when the appropriate length-scale was much larger than the channel thickness. We observed a two-dimensional diffusive conduction mechanism, ...