Showing papers on "Magnetoresistance published in 1978"
TL;DR: In this paper, the Hall effect was used to measure the conduction electron spin polarization in uniaxial materials, where a d.c. eddy-current loop caused by the Hall Effect runs around each wall.
Abstract: Despite common misconceptions, domain walls are too thick to ’’scatter’’ electrons appreciably. However, electrons crossing a wall apply a torque to it, which tends to cant the wall spins. This could be used to measure the conduction electron spin polarization. Most of the low‐field resistive anomalies observed in pure Fe, Ni and Co at low temperature are caused by the Lorentz force associated with the internal field B=Ms present inside each domain. The existence of low‐resistivity paths extending over many domains accounts for still unexplained magnetoresistance data in iron whiskers. In uniaxial materials, a d.c. eddy‐current loop caused by the Hall effect runs around each wall. The field Hz generated by these loops tends to ’’drag’’ the whole domain structure in the direction of the carrier drift velocity. Also, the Joule dissipation of the eddy currents manifests itself as an excess Ohmic resistance. As predicted, this excess resistance decreases as the square of the field, in amorphous Gd25Co75 films...
367 citations
TL;DR: In this article, a simple two-band model was proposed to account for the temperature dependence of these quantities as well as the magnetic field dependence of the Hall constant in the Ohmic regime below 58 K.
Abstract: The charge-density-wave (CDW) linear-chain metal Nb${\mathrm{Se}}_{3}$ shows striking non-Ohmic behavior when the applied electric field exceeds \ensuremath{\sim} 0.1 V/cm. Hall effect, transverse magnetoresistance, conductivity anisotropy, and Shubnikov-de Haas measurements using sufficiently low current densities to avoid Ohmic breakdown have been published. We propose a simple two-band model to account for the temperature dependence of these quantities as well as the (magnetic) field dependence of the Hall constant in the Ohmic regime below 58 K. The model has six unknowns (carrier concentrations and mobilities) that are fixed by six experimental numbers at each temperature $T$. The solution shows that all the mobilities obey a power-law behavior versus $T$, whereas the carrier concentrations are both $T$ independent up to 40 K. Above 40 K the hole population rises sharply, analogous to the theoretical predictions for an excitonic insulator. This implies that the CDW gap occurs on the hole surface. Using the parameters of the model, we have recomputed the resistivities, Hall constant, and magnetoresistance, and they have been shown to agree with all the available experimental data. Thus the conventional single-particle picture with the additional hypothesis of a BCS-type gap on the hole surface is adequate for understanding the transport properties of Nb${\mathrm{Se}}_{3}$ in the zero-frequency-Ohmic regime. We also interpret the SdH data in terms of the two-band model.
49 citations
TL;DR: In this paper, the magnetic properties of amorphous Ni1-cPc alloys in the concentration range 0.5
Abstract: Presents the results of an experimental study of electrodeposited amorphous Ni1-cPc alloys in the concentration range 0.5
37 citations
TL;DR: In this article, the resistivity of n-type indium antimonide down to 0.3K was measured in a magnetic field (0-40 kG) both parallel and perpendicular to the current.
Abstract: Measurements on n-type indium antimonide down to 0.3K are described of the resistivity in a magnetic field (0-40 kG) both parallel and perpendicular to the current, and of the Hall effect. Increases of resistivity by a factor of 1010 are observed before the resistivity becomes too high to measure provided special care is taken over the preparation of the surface of the specimen. A saturation of resistivity with increase of magnetic field is sometimes observed and this is attributed to the effect of a conducting surface layer. The resistivity approximates to the form rho -1= rho 01-1 exp(-E1/kT)+ rho 03-1 exp(-E3/kT). The E1 region is identified with magnetic freeze-out and the E3 region with electrons hopping between donor centres. Good agreement is obtained between theory and experiment for the magnetic field dependence of rho 03.
37 citations
TL;DR: In this article, the magnetoresistance of itinerant electron antiferromagnets is studied on the basis of the two band model where the electrons in one conduction or s-band are the current carriers and are scattered by the spin fluctuations due to the d electrons.
Abstract: The magnetoresistance of itinerant electron antiferromagnets is studied on the basis of the two band model where the electrons in one conduction or s-band are the current carriers and are scattered by the spin fluctuations due to the d electrons. The self-consistent renormalization theory of spin fluctuations is applied to the d electrons. The resistivity shows a cusp at the Neel temperature and becomes linear in T at high temperatures. The resistivity under a perpendicular field shows a negative magnetoresistance for small fields and a narrow peak at the antiferromagnetic to paramagnetic transition point H c . In the case of a parallel applied field with the uniaxial anisotropy, we expect a large increase in the magnetoresistance on both sides of the spin flopping transition point. Numerical calculations are made with the use of the free electron gas model with Umklapp processes.
34 citations
TL;DR: In this paper, a negative magnetoresistance effect was observed in n-channel inversion layers in Cs covered p-Si(111) surfaces at temperatures between 1.4 and 20 K.
27 citations
TL;DR: In this paper, it was shown that Tetrathiatetracene 2(iodine)3 is a stable organic metal down to 3.3 K. The results obtained indicate a metallic state at high temperatures, but also support a nonmetallic state at temperatures below 30 K. At 20-30 K, a metal-to-insulator phase transition occurs.
Abstract: A recent investigation in which Isett and Perez-Albuerne (1977) found that (tetrathiatetracene)2(iodine)3 is a stable organic metal down to 3.3 K is of considerable interest. In view of the diversity of suggestions made regarding this compound, measurements, were made of its electrical, magnetic, and optical properties. The results obtained indicate a metallic state at high temperatures, but also support a nonmetallic state at temperatures below 30 K. At 20-30 K, a metal-to-insulator phase transition occurs. This is indicated by the onset of a large and positive magnetoresistance, the leveling off in the temperature dependence of the ESR linewidth, and by recent derivative analysis of the electrical conductivity in this region. The investigated compound represents an interesting one-dimensional electronic system in which it may be possible to study the combined effects of disorder and interchain coupling on charge transport processes.
27 citations
TL;DR: The negative transverse magnetoresistance effect was observed in n -inversion layers in Si-MOS (111) surfaces at temperatures between 1.5 and 8.3 K as discussed by the authors.
26 citations
TL;DR: In this paper, low temperature magnetoresistance measurements on weakly doped tellurium samples (p 15 cm −3 ) show a large number of structures which appear only under non-ohmic conditions.
Abstract: Low temperature magnetoresistance measurements on weakly doped tellurium samples ( p 15 cm −3 ) show a large number of structures which appear only under nonohmic conditions. Depending on the electric field strength and the chemical nature of the impurities, different types of structures in the magnetoresistance are visible. The most remarkable effect is the appearance of sharp maxima in the magnetoresistance (halfwidth ΔB ∼ 0.07 T) which show up at relatively low electric fields of about 1 V/cm. The magnetic field positions of these peaks are correlated with the chemical nature of the impurities. The resonance appears for the different impurities at B = 3.40 T (Bi), B = 3.61 T (Sb), and B = 3.77 T (As)( B ⊥ c ). Further structures in the magnetoresistance under hot carrier conditions are correlated with a resonance between the lowest impurity excitation energy and the cyclotron resonance energy. From hot magnetophonon measurements, impurities with quite different binding energies could be identified.
23 citations
TL;DR: In this paper, the influence of a magnetic field dependence of the valley splitting in n-type inverted (100) silicon MOSFET surfaces is observed for the first time from an abrupt phase shift for the position of the Shubnikov -de Haas extrema in the osciallatory magnetoresistance at constant gate voltages.
23 citations
01 Jan 1978
Patent•
19 Oct 1978TL;DR: In this paper, a pick-up device for reading out information which has been recorded on a magnetic medium is described, where a substrate and a layer of soft magnetic material overlying a surface of the substrate, the easy axis or direction of magnetization being normal to the surface and the magnetic material having properties capable of having magnetic bubble domains generated and propagated therein, so that patterns of magnetic domains are formed in the layer of magnetic material corresponding to the patterns of recorded information.
Abstract: A pick-up device for reading out information which has been recorded on a magnetic medium. The device comprises a substrate and a layer of soft magnetic material overlying a surface of the substrate, the easy axis or direction of magnetization being normal to the surface and the magnetic material having properties capable of having magnetic bubble domains generated and propagated therein, so that when the pick-up device is used to read out information from a magnetic medium, patterns of magnetic domains are formed in the layer of magnetic material corresponding to the patterns of the recorded information. Although the magnetic material is of the type capable of having magnetic bubble domains generated and propagated therein, there is no need to provide the usual bias field for maintaining the bubble domains or for providing domain-transport or domain-annihilating fields. In one use of the pick-up device, light is transmitted through the substrate and through the layer of magnetic material to be reflected from a layer of light-reflective material back through the magnetic material and the substrate, whereby the polarization of the reflected light is rotated, relative to the polarization of the transmitted light, by an amount determined by the patterns of magnetic domains formed in the layer of magnetic material. Hence, the recorded information can be optically read from the magnetic medium. In another use of this device, a magnetoresistive head is disposed on the substrate, the resistance of this magnetoresistive head being varied as a function of the patterns of magnetic domains formed in the layer of magnetic material.
TL;DR: In this paper, the transverse magnetoresistance of 1T-TaS2 was measured in magnetic fields up to 100 kOe in the semiconductive region corresponding to the commensurate charge density wave (CDW) state.
Patent•
23 Feb 1978TL;DR: In this paper, a magnetic converter having a magnetoresistive element, the resistance of which is measured by means of an alternating current having a frequency which is larger than 8ρ/μD, where ρ is the resistivity, μ the magnetic permeability and D the cross-section of the element so that the current distribution is concentrated at the edges of the elements due to the resultant lateral skin effect.
Abstract: A magnetic converter having a magnetoresistive element, the resistance of which is measured by means of an alternating current having a frequency which is larger than 8ρ/μD, where ρ is the resistivity, μ the magnetic permeability and D the cross-section of the element so that the current distribution is concentrated at the edges of the element due to the resultant lateral skin effect.
TL;DR: In this article, the magnetoresistance effect in vacuum-evaporated non-magnetostrictive Ni-Fe-Co films in the compositional range 0-40 wt.% cobalt was made.
TL;DR: In this paper, the authors review the available knowledge of the bulk magnetic and transport properties of rare earth metals with a particular emphasis on the ways in which these macroscopic properties may be interpreted to improve understanding of the fundamental microscopic interactions.
Abstract: Publisher Summary This chapter reviews the available knowledge of the bulk magnetic and transport properties of the rare earth metals with a particular emphasis on the ways in which these macroscopic properties may be interpreted to improve understanding of the fundamental microscopic interactions. The chapter discusses the magnetization and susceptibility of these metals followed by their magnetic anisotropy and magnetostriction. The chapter also discusses electrical resistivity and deals with magnetoresistance and the Hall effect. Before reviewing the experimental magnetization and susceptibility data, the chapter outlines the appropriate features of a microscopic theory with which the magnetization is calculated from a detailed knowledge of the spin wave dispersion relations. Such a calculation has recently been carried out for terbium following a comprehensive study of the magnetic excitations in the ferromagnetic phase of this element.
TL;DR: In this article, the isotropic and anisotropic magnetoresistance of dilute alloys of PdFe, PdCo, and PdNi at low temperatures were measured.
Abstract: The isotropic and anisotropic magnetoresistance have been measured for dilute alloys of PdFe, PdCo, PdNi at low temperatures. Physically different effects dominate in each case. In PdFe there is a temperature-dependent negative magnetoresistance from the suppression of electron-magnon scattering. In PdNi there is a positive isotropic magnetoresistance due to the effect of the magnetic field on the magnitude of the Ni moments, plus an anisotropic magnetoresistance arising from local orbital moments in Ni sites. In PdCo there is a negative isotropic magnetoresistance associated with magnetising the sample. The authors suggest that this is due to non-ferromagnetic interactions between Co moments.
TL;DR: In this paper, the influence of pulsed electric fields on the magnetophonon structure in the transverse and longitudinal magnetoresistance of n-InSb at 77 K has been reexamined using a magnetic field modulation technique.
Abstract: The influence of pulsed electric fields on the magnetophonon structure in the transverse and longitudinal magnetoresistance of n-InSb at 77 K has been reexamined using a magnetic field modulation technique. For the transverse configuration, a shift to higher magnetic fields with increasing electric field is observed for the resistance maxima up to N = 8. The amplitudes decrease monotonously and disappear at about 60V/cm for N = 3. In the longitudinal case, the extrema shift to lower magnetic fields as the electric field is increased. In contrast to the transverse case, the amplitudes increase by a factor of 1.8 up to 15V/cm, and then either decrease or become saturated, depending on the harmonic number of the extremum under consideration. These experimental results are discussed within the context of calculations based on a quantum kinetic equation approach and predictions obtained from a simplified analytical theory.
TL;DR: In this paper, the peculiar secondary minimum in the parallel pump butterfly curve for [110] magnetized single crystal YIG has been experimentally and theoretically investigated and data were obtained for an in-plane magnetized YIG.
Abstract: The peculiar secondary minimum in the parallel pump butterfly curve for [110] magnetized single crystal YIG, originally discovered by Sethares and coworkers, has been experimentally and theoretically investigated Data were obtained for an in-plane [110] magnetized
TL;DR: In this article, the quantum limit behavior of magnetoresistance in narrow-gap semiconductors is investigated and the non-parabolicity of the energy dispersion is taken into account in the density of states.
TL;DR: In this paper, the authors measured the lattice thermal conductivity of very pure aluminium in the temperature range between 1.5K and 15K by suppressing the electronic thermal conductivities with a magnetic field in the Corbino geometry.
Abstract: The authors have measured the lattice thermal conductivity of very pure aluminium in the temperature range between 1.5K and 15K by suppressing the electronic thermal conductivity with a magnetic field in the Corbino geometry. Taking into account a linear term in the magnetoresistance in the extrapolation procedure, it is shown that the results are in excellent agreement with results obtained from alloying techniques and theoretical estimates.
TL;DR: Magnetoresistance measurements on PdFe alloys at low temperature show behaviour which is in good qualitative agreement with a dilute ferromagnet model in which electron-magnon scattering does not conserve momentum as mentioned in this paper.
Abstract: Magnetoresistance measurements on 1 at.% and 2.7 at.% PdFe alloys at low temperature show behaviour which is in good qualitative agreement with a dilute ferromagnet model in which electron-magnon scattering does not conserve momentum.
TL;DR: In this article, electrical resistivity and magnetoresistance measurements from 4K to 300K on Metglas 2605 and Metglas2605 A are reported, and the anisotropic magnetoresistivity was found to increase with decreasing temperature.
Abstract: Electrical resistivity and magnetoresistance measurements from 4K to 300K on Metglas 2605 and Metglas 2605 A are reported. For both materials a resistivity minimum appears at low temperatures. Below the minimum an approximately logarithmic increase of resistivity was found. Magnetoresistance measurements were used to get additional information about the electronic conduction, magnetic texture and the nature of the magnetization process in these alloys. The anisotropic magnetoresistivity was found to increase with decreasing temperature.
TL;DR: In this paper, the Hall and magnetoresistive effect in FeSi amorphous films were measured and the spontaneous Hall constant increased as the Si content increases. But the magnetic field was not analyzed.
Abstract: Measurements on the Hall and the magnetoresistive effect in Fe‐Si amorphous films are described. The spontaneous Hall constant Rs increases as the Si content increases. A sensitive irreversible change of Rs was observed by annealing. Rs increases by crystallization. The magnetoresistive effect Δρ/ρ is low but Δρ is comparable to those of Fe‐Ni crystalline alloys.
TL;DR: In this article, it was shown that the random anisotropy model of Harris, Plischke and Zuckermann (HPZ) gives a good description of some magnetic properties of amorphous rare-earth-noble metal alloys.
TL;DR: In this article, the effect of nonparabolic band structure on the transverse magnetoresistance in a semiconductor such as ntype InSb in the presence of a dc magnetic field is studied taking into account the inelasticities in the electron-phonon scattering.
Abstract: The effect of nonparabolic band structure on the transverse magnetoresistance in a semiconductor such as ntype InSb in the presence of a dc magnetic field is studied taking into account the inelasticities in the electron-phonon scattering. We discus's this effect of nonparabolicity in semiconductors for both deformationpotential'coupling and piezoelectric coupling to acoustic phonons. Results show that the numerical values of the transverse magnetoresistance for the case of the piezoelectric c'oupling are much smaller than those for the case of the deformation-potential coupling. Therefore, the deformation-potential coupling mechanism plays the dominant role for the transverse magnetoresistance in strong magnetic fields in n-type InSb. We also found that the nonparabolicity of the energy-band structure will change the effect of the temperature on the transverse magnetoresistance besides the enhancement of its magnitude. Our numerical results are found to be in qualitative agreement with experimental results in the quantum limit.
TL;DR: In this article, the effects due to a rotating magnetic field applied in the sample plane have been studied when the sample is saturated and when it is unsaturated, and they have been used to measure low magnetic fields with the sample acting as a detector.
Abstract: Magnetoresistance measurements have been made in thin films using a special experimental set-up. Effects due to a rotating magnetic field applied in the sample plane have been studied when the sample is saturated and when it is unsaturated, and they have been used to measure low magnetic fields with the sample acting as a detector.
TL;DR: In this article, the consequences of the magnetoconcentration effect on the longitudinal current in semiconductor slabs are investigated over a wide range of magnetic field B. It is shown that the current component resulting from the action of the Lorentz force on the transverse diffusion currents is comparable to the conduction component in Ge and especially InSb, even for moderate values of B.
Abstract: The consequences of the magnetoconcentration effect on the longitudinal current in semiconductor slabs are investigated over a wide range of magnetic field B. It is shown that the current component resulting from the action of the Lorentz force on the transverse diffusion currents is comparable to the conduction component in Ge and especially InSb, even for moderate values of B. The influence of the transverse diffusion remains remarkably important even in the weakest electric fields. Experiments performed at room temperature show good agreement with the developed theory.
TL;DR: In this article, a simple extension of the cubic theory to the case of substrate-induced tetragonal distortion can account for the deviations of weak field magnetoresistance measurements from the requirements of cubic symmetry.
Abstract: Nishiyama’s weak‐field magnetoresistance measurements on p‐type SnTe films deviate substantially from the requirements of cubic symmetry. A simple extension of the cubic theory to the case of substrate‐induced tetragonal distortion can account for the measurements. To establish internal consistency of the data with tetragonal symmetry requires an additional measurement which was not, but can easily be, made.