Hall Coefficient RH Research Articles

Effect of electron-hole scattering on the resistivity and Hall coefficient in YBaCuO

Coupled electron-hole (e-h) Boltzmann equations are applied to evaluate the resistivity ρ and Hall coefficientRH for a two-band model system with e-h, impurity, and phonon scatterings. We show that the anomalous temperature dependences ρ=αT andRH−1=βT observed on YBaCuO compounds can be obtained by assuming a special two-band model in which the e-h scattering is responsible for the resistivity and the chemical potential varies linearly with temperature.

Interplay of the Boltzmann-type ordinary transport and quantum corrections in Ag-Cu-Ge amorphous alloy system. II. Temperature dependence of Hall coefficient

For pt.I see ibid., vol.18, p.1995 (1988). The Hall coefficient RH has been measured for a series of (Ag0.5Cu0.5)1-xGex amorphous alloys in the temperature range 1.5-300 K. The value of RH for x=0.2 is temperature independent over the whole temperature range, whereas that for x=0.5, 0.6 and 0.7 exhibits a T1/2 temperature dependence below about 50 K. The temperature-independent Hall coefficient can be taken as evidence for the negligible contribution of the quantum corrections, lending support to the analysis based on the Boltzmann-type ordinary scattering mechanism for the low-resistivity data in the preceding paper. On the other hand, the square-root temperature dependence of the Hall coefficient provides clear evidence for the dominant role of the electron-electron interaction in high-resistivity alloys.

Optical and transport properties of the Sb2-xInxTe3 single crystals

Single crystals of Sb2-xInxTe3 (x = 0.0-0.4) were prepared from the elements of 5N purity using the modified Bridgman method. On the samples with a various content of incorporated In-atoms the optical properties (reflectivity, transmission) in IR region and the transport coefficients (electrical conductivity σ⊥c, Hall coefficient RH(B || c), Seebeck coefficient S⊥c) were measured. The results showed that the In-atoms incorporated in Sb2Te3 crystal lattice suppress the free carrier concentration. The observed decrease in the hole concentration with increasing content of incorporated In-atoms was explained by the interaction of incorporated In-atoms with antisite defects Sb'Te. The increasing concentration of incorporated In-atoms in the crystal lattice leads to the increase of the bond polarity and to the increase of ionicity of the studied mixed crystals. The consequence of these changes is the decrease of antisite defect concentration.

The Low Field Hall Coefficient of Copper and Palladium

Precise measurements of the low field Hall coefficient RH of pure copper and palladium have been made between 2K and 16 K by the use of SQUID. Residual resistance ratios of the Cu and Pd samples were about 22000 and 1500 respectively. We have deduced the temperature dependence of the relaxation times from the RH and the electrical resistivity data using a two group model. For Cu the relaxation times τ of the neck (N) and the belly (B) regions of the Fermi surface vary as 1/τN∼T3.3 and 1/τB∼T5 and for Pd 1/τh∼T1.9 and 1/τe∼T3, where τh and τe are the relaxation times Γ of the Γ centered electron and the open hole sheets respectively. These results are discussed in terms of the anisotropy of electron-phonon and electron-electron scattering.

Hall effect and the upper critical field in UBe13

The temperature dependence of the Hall coefficient RH(T) in UBe13 was measured down to 0.2 K. When temperature is lowered the Hall coefficient passes through a maximum at T = 2 K and then strongly decreases. The RH(T) sign inversion near the superconducting transition temperature Tc = 0.9 K was observed.

Superconductivity of Ion-Beam-Sputtered Amorphous Beryllium Thin Films

In order to investigate the origin of the Tc enhancement in ion-beam-sputtered Be films, the electronic density of states at Fermi level N(0) was estimated from the temperature dependence of the critical magnetic field Hc2 and the Hall coefficient RH measurements. The Tc dependence on N(0) was discussed by considering BCS's relationship between Tc and N(0). This experiment showed that the Tc enhancement was caused by not only N(0) increment but also other factors.

The Hall effect in liquid mercury-gallium alloys

The Hall coefficient RH of Hg-Ga liquid alloys has been measured, via the Corbino geometry, using Ga as a reference material. Phase separation was avoided by working in the temperature range 490-500K. Disc specimens 1 mm thick were used to ease the problems of preparation and containment. The results have been compared with RH(FE)=-(n mod e mod )-1 which is the value predicted by the free-electron model. It was found that Delta RH/RH(FE)=(RH-RH(FE))/RH(FE) is always negative in the Hg-Ga system, a trend that is observed in other mercury alloys. The authors discuss whether the contribution to RH from skew scattering, caused by spin-orbit interaction, can explain the general behaviour that is found experimentally.

D.c. galvanomagnetic properties in a heavily compensated single crystal of n-type CdTe

Experimental data on d.c. galvanomagnetic properties, namely the Hall coefficientRH, the low-electric-field d.c. conductivityσ and the Hall mobilityμH, in a heavily compensated single crystal of n-type CdTe in the temperature range 77 to 300 K have been analysed, firstly on the basis of a simple one-band model involving normal free-electron conduction, and secondly on the basis of a two-band model involving normal free-electron conduction along with impurity-band conduction. The analysis provides evidence for a significant contribution of impurityband conduction to the transport phenomena at temperatures below ∼ 150 K. This conclusion is further substantiated by transverse magnetoresistance measurements and the observed dependence of d.c. conductivity on the electric field. From the analysis of these data, the average hopping distanceR in the impurity band is calculated, and it is found to increase with decrease of temperature. The relative contributions of normal free-electron conduction and impurity-band conduction to the d.c. galvanomagnetic properties are estimated at different temperatures.

Temperature- and magnetic field dependence of the Hall effect in the heavy fermion system CeCu6

The temperature dependence of the Hall coefficient and the magnetic field dependence of the Hall resistivity of CeCu6 have been determined in the temperature range 80 mK<T<10 K and in magnetic fields up to 10T. The Hall coefficientRH shows a very strong temperature dependence with two extrema and a change of sign, and the Hall resistivity ρxy has a strong field dependence with up to two changes of sign. The observed behavior can partially be explained by the field- and temperature dependence of the skew scattering contribution to the Hall coefficient.

Size effect in the low-field Hall coefficient of single-crystal copper films

Measurements of the low-field Hall coefficientRH of single-crystal copper films were made at 4.2 K by the use of a SQUID. The surface normaln of the samples was directed in the [100], [110], and [111] directions and the ratio of the thickness to the mean free path ranged from 0.1 to 0.7. It is found that the effect of surface scattering causesRH to decrease whenn ‖ [100], whereas it causesRH to increase whenn ‖ [110] and [111]. This behavior is interpreted in terms of the geometrical characteristics of the Fermi surface.

Concentration and temperature dependence of the Hall resistivity in FeZr glasses

Hall resistivity measurements are reported for amorphous FexZr1−x alloys near the critical concentration, xc =0.37, for the onset of ferromagnetism. At room temperature, the Hall coefficient RH is positive and grows systematically with Fe concentration as xc is approached from the paramagnetic side. The temperature dependence of RH follows a Curie-like variation whose coefficient diverges at xc. In the ferromagnetic regime, the spontaneous Hall coefficient is extremely large, leading to the conclusion that the side-jump mechanism is responsible for the magnetic contribution. Furthermore, the dependence of RH on susceptibility in the two regimes suggests that this same side-jump term is also responsible for the positive Hall coefficient in the nonmagnetic glasses.

金属間化合物HgTeの電流磁気効果とその解析

The Hall coefficient RH and the magneto-resistance Δρ⁄ρ0 were measured near 4.2 K on HgTe single crystals annealed at 553-723 K in the Hg vapour of 300 Pa-500 kPa.RH and Δρ⁄ρ0 showed the dependence upon the magnetic field in the range between 0 and 960 kA/m. Analyzing these results by the two carrier model, the carrier concentrations, Ne and Nh, and the carrier mobilities, μe and μh, were obtained. The subscripts e and h refer to electron and hole, respectively. Ne was in proportion to Hg vapour pressure PHg, while Nh was in reverse proportion to that in the experimental range of PHg. μe and μh had the maximum μe∗ and μh∗ at almost the same PHg∗, respectively. Both varied in proportion to PHg1⁄2 in the case of PHg<PHg∗, but to PHg−1⁄2 in the reverse case. The concentration product Ne·Nh was calculated at different temperatures and found to be constant independent of temperature, even though the crystals were annealed at different temperatures and pressures. The value of Ne·Nh⁄T3 was plotted against 1⁄T, and then thermal energy gap Eg=−0.32 meV was obtained from the slope of the curve. The negative value suggested that HgTe behaved as semimetallic.

金属間化合物HgTeの水銀あるいはテルル雰囲気処理効果

A single crystal of HgTe was grown by the Bridgman method and annealed in Hg or Te vapour. The Hall coefficient and the electrical conductivity were measured on the annealed crystals in the temperature range between 77 K and room temperature. The electrical conductivity increased with annealing partial pressure. The p-n turning temperature of the sign of the Hall coefficient. RH of Hg-annealed crystal fell with increasing Hg partial pressure, while that of Te-annealed crystal rose. The carrier concentration was calculated from the Hall coefficient RH in the temperature range of exhausion near 77 K by a single carrier model. The Hg partial pressure of p-n transition was obtained from the dependence of carrier concentration upon the Hg partial pressure. The i-boundary corresponding p-n transition and lines of equivalent carrier concentration were drawn on the P-T phase diagram for the Hg-Te system.

Electric and magnetic properties of the Kondo-lattice compound CeCu2Si2

Electric, magnetic, and thermoelectric properties of CexLa1−xCu2Si2 (0⩽x⩽1) compounds have been studied over a wide temperature interval 0.04 ⩽T⩽300 K in magnetic fieldsH⩽40 kOe. The paramagnetic-magnetic ordering transition temperatureTM is found to rise from ∼0.32 K for cerium concentrationx=0.2 to 1.6 K forx=0.6. A further increase inx from ∼0.8 to 1.0 leads to a decrease inTM. Simultaneously, the susceptibility kink is smeared out and atx≈1.0 it is transformed into temperature-independent enhanced Pauli paramagnetism. The magnetic phase diagram has been found to be similar to that proposed by Doniach for the one-dimensional Kondo-necklace model. The Kondo-lattice compound CeCu2Si2 exhibits a superconducting transition atTc⋍0.5 K. The variation of the magnetic properties of CexLa1−xCu2Si2 from magnetic ordering at 0.2≲x≲0.8 to the nonmagnetic superconducting state atx → 1.0 is caused by the crossover from the magnetic regimeTRKKY≫TK (in which the RKKY temperatureTRKKY exceeds the Kondo temperatureTK) to the nonmagnetic singlet ground state corresponding to the situation whenTK≫TRKKY. This crossover is accompanied by a sharp increase in the low-temperature Hall coefficientRH(T) in CexLa1−xCu2Si2 compounds atx → 1. At the same time, a minimum of the negative Seebeck coefficient with a high amplitude appears at 10 pKL, a continuous transition from the Kondo lattice to the intermediate valence state is observed, which is accompanied by a complete smearing out of the resonance near the Fermi level. Therefore the Kondo lattices represent a new class of solids, which can be characterized as the link between stable magnetism of metals with a deep 4f level and unstable magnetism associated with fluctuating valence. This novel state can be described by a set of anomalous low-temperature properties related to the giant Abrikosov-Suhl resonance near the Fermi level.

The influence of electron-libron scattering on the transport properties of quasi-one-dimensional metals

Starting from the formalism of force-correlation functions the electrical resistivity R, the thermoelectric power S and the Hall coefficient RH are calculated for a system containing electron-libron scattering. In the framework of a two-band model these transport quantities can be calculated in the case of weak scattering and high temperatures. The results obtained for R, S and RH are compared qualitatively with measurements on TTF-TCNQ.

Effect of indium on the field effect studies of thin SnTe films

Field effect studies were made on In-rich SnTe films using metal-insulator-semiconductor (silver-mica In-Sn e) structures. It has been observed that when a negative gate field (∼1.5×105V/cm) was applied to the films at 77 K, a permanent decrease in the value of the Hall coefficient RH takes place, whereas no such effect has been noticed in metal-insulator-semiconductor structures on undoped SnTe films.

THE EMPIRICAL CORRELATIONS BETWEEN PHONON SPECTRUM PARAMETERS λ,〈ω〉,〈ω2〉 AND THE HALL COEFFICIENTS OF AMORPHOUS SUPERCONDUCTORS

It is found that there is an empirical correlation between phonon spectrum parameters λ, 〈ω〉,〈ω2〉 and the Hall coefficients RH in a variety of nontransition metals and alloys; there is a maximum of λ,〈ω〉 and 〈ω2〉 as RH =-3.5--4.0×10-11m3/As. There is also a similar empirical correlation between λ, 〈ω〉, 〈ω2〉 and Hall coefficients RHL of responding liquid metals. Finally, the question of raising Tc of amorphous superconductors is discussed.

5227. Novel charged particle analyser for momentum determination in the multichanneling mode. II. Physical realization, performance tests, and sample spectra: H A Engelhardt et al,Rev Sci Instrum,52 (8), 1981, 1161–1173

The Hall-coefficient RH and the electrical resistivity of Cr-Ni alloys was measured at room temperature and −165°C. An alloy with 3.6 at. % Ni showed at −165°C the highest RH value. It was found that the RH values of Cr-Ni alloys were similar to those found for Cr-Fe alloys, if plotted as a function of electron concentration.

AN EMPIRICAL CORRELATION BETWEEN SUPERCONDUCTING ENERGY GAPS 2△0 AND THE HALL COEFFICIENTS IN AMORPHOUS SUPERCONDUCTORS

An empirical correlation between superconducting energy gaps 2△0 and the Hall coefficients RH of amorphous state and between superconducting energy gaps 2△0 of amorphous state and the Hall coefficients RHL of corresponding liquid metals is found respectively, that is: in numerous non-transition metals and alloys, 2△0 takes a maximum value as RH (or RHL)=-3.5--4.0×10-11m3/AS.

High-magnetic-field Van der Pauw method Magnetoresistance measurement and applications

The paper develops a simple theory to account for the magnetoresistance influence on Van der Pauw-type experiments (i.e. resistivity and Hall coefficient RH measurements in arbitrarily shaped samples). In particular, it is proved that the voltage developed between two nonsuccessive contacts includes not only the usual Hall term (involving the magnetic field and RH) but also an additional term proportional to the magnetoresistance coefficient. This term is especially important under high magnetic fields and in anisotropic or ambipolar semiconductors; if ignored, it will be responsible for misleading interpretations of the Hall coefficient behaviour. Moreover, the influence of contact dimensions is shown to result mainly in an erroneous term, proportional to the Hall voltage. In this new light averaging techniques, suitable for more accurate measurements, are proposed. The experimental results fully support the theoretical derivations. As an application, a powerful method for the characterisation of ambipolar semiconductor slabs with arbitrary geometry is presented.