Showing papers on "Magnetoresistance published in 1982"
TL;DR: In this paper, the electrical, magnetic, and optical properties of diluted magnetic semiconductors (often referred to as ‘semimagnetic’) have been reviewed, and the presence of substitutional magnetic ions in these alloys leads to spin-spin exchange interaction between localized magnetic moments and the band electrons.
Abstract: This paper reviews the electrical, magnetic, and optical properties of diluted magnetic semiconductors (sometimes also referred to as ‘‘semimagnetic’’ semiconductors). These materials are ternary semiconductor alloys whose lattice is made up in part of substitutional magnetic ions. Cd1−xMnxTe and Hg1−xMnxTe are examples of such systems. As semiconductors, these alloys display interesting and important properties, such as the variation of the energy gap and of effective mass with composition. They also exhibit magnetic properties which are interesting in their own right, e.g., a low temperature spin glass transition and magnon excitations. Most importantly, however, the presence of substitutional magnetic ions in these alloys leads to spin–spin exchange interaction between the localized magnetic moments and the band electrons. This in turn has rather important consequences on band structure and on donor and acceptor states, leading to dramatic effects in quantum transport, impurity conduction, and magneto‐optics. Specifically, the presence of exchange interaction results in extremely large and temperature dependent g‐factors of electrons and holes; in gigantic values of Faraday rotation; in anomalously large negative magnetoresistance; and in the formation of the bound magnetic polaron.
352 citations
TL;DR: In this paper, the magnetoresistance in the two-dimensional electron gas of silicon metal-oxide-semiconductor field effect transistor inversion layers at temperatures down to 50 mK was studied and clear evidence for localization and correlation effects was observed in the region of resistance.
Abstract: We have studied the magnetoresistance in the two-dimensional electron gas of silicon metal-oxide-semiconductor field-effect transistor inversion layers at temperatures down to 50 mK. Both low- and high-mobility samples have been studied and clear evidence for localization as well as correlation effects is observed in the region of resistance ${R}_{\ensuremath{\square}}\ensuremath{\ll}10$ k\ensuremath{\Omega}/\ensuremath{\square}. From detailed fits of the data at low magnetic fields a localization parameter $\ensuremath{\alpha}$ as well as the temperature dependence of the inelastic scattering rate is extracted. From the data we conclude that the dominant inelastic scattering mechanism at these temperatures is electron-electron scattering in the dirty limit. At higher fields correlation effects dominate and the associated parameters are determined.
116 citations
TL;DR: In this article, the effects of intra-state correlation on the variable range hopping were investigated in the absence and presence of a magnetic field, and the intrastate correlation was found to have a linear dependence on the magnetic field in lower magnetic fields.
Abstract: Effects of intra-state correlation on the variable range hopping are investigated in the absence and presence of a magnetic field. In the absence of a magnetic field, Mott's expression for the resistivity, ρ∝exp [ T 0 / T ] 1/4 , still holds in its temperature dependence. However, the prefactor T 0 now depends on two types of localization lengths brought about by the intra-state correlation. Magnetoresistance is found to be positive due to the intra-state correlation. It shows a linear dependence on a magnetic field in lower magnetic fields and saturates above a certain magnetic field.
110 citations
TL;DR: In this paper, the authors generalize the Mooij rule for disordered metals and find that the temperature dependence of the conductivity sigma of disordered metal as a function of temperature must change slope due to diffusion effects, and if interaction effects are included, sigma changes its slope three times.
Abstract: The authors generalise the Mooij rule (1973) for disordered metals. They find that the temperature dependence of the conductivity sigma of a disordered metal as a function of temperature must change slope due to diffusion effects, and if interaction effects are included, sigma changes its slope three times. The crossover temperature (if it occurs at high temperatures) from positive to negative d sigma /dT due to diffusion effects varies as C5, where C is the average concentration of impurities or scattering centres. Another crossover temperature which separates electron correlation effects from diffusion effects is predicted. This explains the temperature dependence observed for Ge1-xAux. It is also shown that the non-metallic behaviour of the AC conductivity is accounted for by diffusion effects and there is no need to invoke the concept of a pseudogap due to electron interaction. The negative magnetoresistance follows from the theory for diffusion effects in agreement with the perturbation theory of Kawabata (1980).
108 citations
TL;DR: In this paper, the authors discuss the transport properties of transition ferromagnetic alloys and their alloys, focusing on the internal magnetoresistance of Fe, Co, and Ni.
Abstract: Publisher Summary This chapter discusses the transport properties of ferromagnets. The focus is on transport properties of the transition ferromagnets Fe, Co, and Ni and their alloys. In pure ferromagnetic metals, the “internal magnetoresistance” enhances the resistivity that is no longer proportional to the concentration of impurities. This effect is particularly important for Fe and a high transverse magnetoresistance. For demagnetized Fe polycrystals, it was pointed out that the apparent residual resistivity ratio would never increase beyond about 300, however pure the sample. It is now standard practice to measure the low temperature resistivity of Fe samples in a saturating longitudinal magnetic field to eliminate transverse magnetoresistance. This can reduce the apparent resistivity by a factor of five or more. In principle, a correction should still be made for the longitudinal magnetoresistance. In Ni samples, the enhancement of the residual resistivity by the internal magnetoresistance is less important than in Fe but still significant. For non-magnetic alloys, the low temperature magnetoresistance behavior generally follows Kohler's rule. Schwerer and Silcox showed by a careful study of dilute Ni alloy samples that for a given series of alloys the ordinary magnetoresistance follows a Kohler's rule, but that the Kohler function varied considerably with the type of scatterer.
105 citations
TL;DR: In this paper, the magnetization and magnetoresistance of itinerant electron helical magnet MnSi was studied down to 0.45 K and the existence of two new phases were suggested.
Abstract: Magnetization and magnetoresistance of itinerant electron helical magnet MnSi has been studied down to 0.45 K. A large negative magnetoresistance is observed especially around Neel temperature T N in accord with the theoretical expectation. Below 1 K, however, a positive magnetoresistance is found and it is attributed to the normal magnetoresistance due to impurity scattering. Anomalous peaks in the magnetization and magnetoresistance are observed just below T N between about 1.0 and 2.2 kOe and the existence of two new phases are suggested.
95 citations
TL;DR: The magnetoresistance of pure graphite has been measured at low temperatures down to 0.48 K, under a steady magnetic field up to 28.5 T with the use of a hybrid magnet as mentioned in this paper.
Abstract: The magnetoresistance of pure graphite has been measured at low temperatures down to 0.48 K, under a steady magnetic field up to 28.5 T with the use of a hybrid magnet. A striking anomaly in the magnetoresistance was found at fields above 22 T. The fact that the critical field of the anomaly has a strong temperature dependence suggests the onset of an electronic phase transition, and makes an explanation of this phenomenon in terms of known one-electron properties of graphite unlikely.
76 citations
72 citations
TL;DR: In this paper, resistivity measurements along the high conductivity axis of (TMTSF)2AsF6 for various hydrostatic pressures up to 12 kbar, and for transverse magnetic fields of up to 70 kOe, in the temperature range 0.1 K-300 K.
Abstract: 2014 We report resistivity measurements along the high conductivity axis of (TMTSF)2AsF6 for various hydrostatic pressures up to 12 kbar, and for transverse magnetic fields of up to 70 kOe, in the temperature range 0.1 K-300 K. We derive a phase diagram which shows a « triple » point near Tc = 1.22 K and Pc = 10.5 kbar, and a reentrant behaviour of the superconducting state inside the semiconducting state. Moreover we observe a striking anisotropy in the transverse critical fields Hc2 and large changes in these fields near the « triple » point. These features suggest we are dealing, in these compounds, with non usual superconducting properties. The transverse magnetoresistance also shows very interesting features including a large anisotropy and a very similar behaviour in the conducting and semiconducting phases. These peculiarities might be rationalized if one assumes (on account of the low dimensionality of the electron system) that first the superconducting instability can grow from below about 30 K and secondly that it can coexist to some extent with the competing SDW instability responsible for the semiconducting phase due to the existence of significant electron-electron couplings. J. Physique 43 (1982) 801-808 m 1982,
69 citations
TL;DR: In this paper, the characteristics of carbon-glass resistance thermometers for temperatures from 2.15 to 320 K and in magnetic fields of up to 19 T are described. But the results from nine thermometers made from six different batches of raw material are combined to produce mean values that may be used to correct a "typical" thermometer at 19 T to within ± 0.1% in temperatures between 30 and 320 K.
Abstract: The characteristics of carbon‐glass resistance thermometers for temperatures from 2.15 to 320 K and in magnetic fields of up to 19 T are described. The results from nine thermometers made from six different batches of raw material are combined to produce mean values that may be used to correct a ’’typical’’ thermometer at 19 T to within ±0.1% in temperatures between 30 and 320 K, and to within ±1% between 2.15 and 30 K. All nine sensors show a small orientation dependence of their magnetoresistance at 77 K; two out of four tested have an experimentally significant dependence at 4.2 K. The temperature error corresponding to the magnetoresistance of a miniature precision platinum resistance thermometer at 19 T is less than for carbon‐glass sensors above 77 K. New recommendations are made for the optimum use of low‐temperature thermometers in high magnetic fields.
64 citations
TL;DR: Magnetoresistance (ρxx) and Hall resistance (ρxy) measurements on GaAs-AlxGa1−xAs heterostructures demonstrate that in the temperature limit T → 0 not all states of a Landau level are localized as discussed by the authors.
TL;DR: In this paper, the field dependence of the resistance of thin Mg films was measured and the absolute value of the magnetoconductance agreed well with the theory, and the temperature dependence of inelastic scattering time was determined.
Abstract: The field dependence of the resistance of thin Mg films ($50lRl200\frac{\ensuremath{\Omega}}{\ensuremath{\square}}$) is measured. The field dependence allows a quantitative analysis of the weak localization. The absolute value of the magnetoconductance agrees well with the theory. The temperature dependence of the inelastic scattering time is determined.
TL;DR: In this article, the exact diagonalization of the model was used to calculate the resistivity for arbitrary magnetic fields at zero temperature, and the resistivities were then used to estimate the magnetic field resistivity at any temperature.
TL;DR: In this paper, the electrical properties of thin Cu films with resistance per square in the range 1 to 100 ϵ ϵπ ϵ-square have been studied and the results are in good agreement with the predictions of Abrahams et al. for localization in two dimensions.
Abstract: The electrical properties of thin Cu films with resistance per square in the range 1 to 100 $\frac{\ensuremath{\Omega}}{\ensuremath{\square}}$ have been studied. For temperatures below 10 K, the resistance of the films increases logarithmically with decreasing temperature and the magnitude of the rise becomes larger as the resistance per square is increased. The results are in good agreement with the predictions of Abrahams et al. for localization in two dimensions. The effect of a magnetic field has also been investigated. The negative magnetoresistance observed in a perpendicular field is in good agreement with the recent theory of Altshuler et al.: At low fields ($Hl{10}^{\ensuremath{-}2}$ T), no magnetoresistance is observed; for ${10}^{\ensuremath{-}2}\mathrm{T}lHl1$ T the magnetoresistance changes logarithmically with the magnetic field. For very high fields ($H\ensuremath{\gtrsim}5$ T), localization is destroyed, as predicted by theory. In a field parallel to the film plane no negative magnetoresistance is observed. A detailed analysis of the results indicates that spin-orbit effects (of moderate strength) must be taken into account.
TL;DR: In this paper, strong spin-orbit scattering and Coulomb interactions are investigated for conductivity of two-dimensional disordered systems, where the Coulomb interaction is positive for both orientations of magnetic field relative to the system, but the characteristic fields are different.
Abstract: Interplays between strong spin-orbit scattering and Coulomb interactions are investigated for conductivity of two-dimensional disordered systems. Magnetoresistance is positive for both orientations of magnetic field relative to the system, but the characteristic fields are different.
TL;DR: In this article, the magnetic properties of permalloy/molybdenum/permalloy sandwiches are investigated and the effect of lamination is found to decrease with the number of layers.
Abstract: A new way of detecting very small magnetic fields is presented, using the magnetoresistance effect of laminated permalloy. The magnetic properties of permalloy/molybdenum/permalloy sandwiches are investigated. It was found that for molybdenum layers above ca. 1000 A the effect of lamination decreases. Model calculations about the magnetic structures are presented. The calculated results agree with the experimental results.
TL;DR: In this article, the authors studied the resistivity, magnetoresistance, magnetostriction and specific heat of a sample of Y4Co3 and confirmed the existence of a superconducting transition at T approximately 2.5K.
Abstract: The authors have studied the resistivity, magnetoresistance, magnetostriction and specific heat of a sample of Y4Co3. They confirm the existence of a superconducting transition at T approximately 2.5K; specific heat data show that at least 20% of the sample becomes superconducting. They also find local moment effects, an exceptionally strong magnetoresistance and orbital effects.
TL;DR: The magnetoresistance and Hall coefficient in the charge-density-wave (CDW) state of 2 H -NbSe 2 and 2 H-TaSe 2 have been measured at low temperatures in magnetic fields up to 150 kOe, using high-quality single crystals as discussed by the authors.
Abstract: The magnetoresistance and Hall coefficient in the charge-density-wave (CDW) state of 2 H -NbSe 2 and 2 H -TaSe 2 have been measured at low temperatures in magnetic fields up to 150 kOe, using high-quality single crystals. The results on these two compounds have been compared with those on 2 H -NbS 2 which has no CDW transition. By the comparison, several anomalous features in the CDW systems (2 H -NbSe 2 and -TaSe 2 ) have been made clear: 1) The magnetoresistance is relatively large and exhibits a linear dependence on magnetic field. 2) The Hall coefficient shows a strong field dependence including a minimum. We consider that the observed behaviors in the CDW systems may be explained by reconstruction of the Fermi surface in the CDW state and magnetic breakdown through the CDW gaps,
TL;DR: Magnetoresistance effects have been studied for graphitising carbon fibres heat-treated stepwise between 1100 degrees C and 3000 degrees C in this article, and the results indicate that a higher degree of graphitisation is attainable for the fibres.
Abstract: Magnetoresistance effects have been studied for graphitising carbon fibres heat-treated stepwise between 1100 degrees C and 3000 degrees C. The original carbon fibres were prepared by benzene decomposition at about 1100 degrees C. The relationship between the transverse magnetoresistance and heat treatment temperature (HTT) at a constant magnetic field is similar to that for other graphitising carbons. The positive magnetoresistance effect observed in the high HTT range for the present fibres is much stronger than that for the mesophase-pitch based carbon fibre possessing the highest graphitisability amongst commercial carbon fibres and even stronger than that for bulk graphitising carbons. The results indicate that a higher degree of graphitisation is attainable for the fibres. The effect of the orientation of the magnetic field on the magnetoresistance has been investigated in relation to the fibre structure.
TL;DR: In this paper, the superconducting interactions coexist with strong magnetic correlations up to about 5.5K in Y9Co7, a hybrid state with some very interesting magnetic properties.
Abstract: The new results of resistance, low-field magnetoresistance and AC susceptibility measurements in Y9Co7 show that the superconducting interactions coexist with strong magnetic correlations up to about 5.5K. This hybrid state has some very interesting magnetic properties.
TL;DR: In this article, a theory of the open-orbit magnetoresistance of potassium was developed and the open orbits caused by the multiple periodicities of a charge-density-wave (CDW) state were derived.
Abstract: A theory of the open-orbit magnetoresistance of potassium, discovered by Coulter and Datars, is developed. The open orbits caused by the multiple periodicities of a charge-density-wave (CDW) state are derived. Since a single crystal consists of domains, each having its CDW wave vector along one of 24 preferred axes, we employ effective-medium theory to calculate the magnetoresistance rotation pattern. The effects of domain texture and size are illustrated. The magnetic field at which open-orbit peaks appear depends on the domain size, which we find to be \ensuremath{\sim}0.1 mm. The rotation pattern at 24 T is calculated in order to exhibit the detailed information that becomes available at extremely high fields. High-field experiments would aid in the determination of open-orbit directions and allow magnetic-breakdown studies of the energy gaps.
TL;DR: In this article, the temperature and magnetic field dependences of resistivity of metallic n -InSb with carrier concentration, n, 1×10 14 cm -1 \(n{\lesssim}n{\sim}9{\times}10^{14}\) cm −1, have been analyzed by taking into account both effects of localization and interaction.
Abstract: The temperature and the magnetic field dependences of resistivity of metallic n -InSb with carrier concentration, n , 1×10 14 cm -1 \({\lesssim}n{\lesssim}9{\times}10^{14}\) cm -1 , have been analysed by taking into account both effects of localization and interaction. The present theory explains characteristic features of the resistivity in such metallic samples.
TL;DR: In this paper, the authors measured the electrical resistivity from 2.8 K to 300 K and the magnetoresistance at 4.2 K with respect to single crystals of Nb 3 S 4 and discussed its behavior in terms of the electron-electron Umklapp scattering.
TL;DR: In this paper, the electrical conductivity of thin Pt films is measured as a function of temperature, magnetic field and electric field, and a logarithmic temperature dependence is observed.
Abstract: The electrical conductivity of thin Pt films is measured as a function of temperature $T$, magnetic field $B$, and electric field $E$. A logarithmic temperature dependence is observed. The magnetoresistance is positive and anisotropic, increasing as $\frac{{B}^{2}}{T}$ in small perpendicular fields and logarithmically in high ${B}_{\ensuremath{\perp}}$. The electric field causes the resistance to drop proportional to ${E}^{2}$ at low $E$ and logarithmically at high $E$, in agreement with localization theory. Our data on the magnetoresistance, however, disagree with theory.
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09 Dec 1982TL;DR: In this article, the first and second magnetic patterns are constructed by alternately and irregularly arranging strong magnetic field generating areas and weak magnetic fields generating areas, respectively, in order to obtain a minimum resistance value and a maximum resistance value, respectively.
Abstract: A pulse coder comprises a rotating member (1) on which first and second magnetic patterns (221, 222; 221', 222') are formed and a fixed member (3) on which first and second magnetoresistance patterns (MR5, MR6) are formed. When the first and second magnetic patterns of the rotating member directly face the first and second magnetoresistance patterns, respectively, of the fixed member, the first and second magnetoresistance patterns have a minimum resistance value and a maximum resistance value, respectively. The first and second magnetic patterns are constructed by alternately and irregularly arranging strong magnetic field generating areas and weak magnetic field generating areas.
TL;DR: In this paper, the magnetoresistance, Hall effect and nonlinear conductivity characteristics in pure and radiation damaged TMTSF>2PF6 were measured and the material below the metal-insulator transition temperature was best described as quasi-two-dimensional with a very high mobility.
Abstract: We have measured the magnetoresistance, Hall effect and the nonlinear conductivity characteristics in pure and radiation damaged (TMTSF>2PF6. We find that the material below the metal-insulator transition temperature is best described as quasi-two-dimensional with a very high mobility (105 cm2/volt-sec). The nonlinear conductivity is suppressed by the application of a magnetic field and by radiation damage. The magnetoresistance, metal-insulator transition temperature and the superconducting transition temperature are also reduced by radiation damage of order 1000 ppm for the latter and 100 ppm for the former.
TL;DR: In this paper, the results of a band structure calculation for the equiatomic B2 (CsCl) CoGa alloy are presented and discussed with reference to data obtained from electrical resistivity, magnetoresistance and Hall effect measurements on CoxGa100-x (40
Abstract: The results of a band structure calculation for the equiatomic B2 (CsCl) CoGa alloy are presented and discussed with reference to data obtained from electrical resistivity, magnetoresistance and Hall effect measurements on CoxGa100-x (40
TL;DR: In this paper, the temperature dependences of the electrical resistivity of sputterd Cu-SiO2 films measured in the range 4-300 K showed minima which depend on the composition.