高压下锐钛矿TiO2的电阻率及能带结构的研究

应用在位电阻率测量方法研究高压下锐钛矿TiO2的电学性质。通过研究电阻率随压力变化的异常变化点,观察到了TiO2从锐钛矿－柯铁矿－斜锆石的相变。卸压后,电阻率数值和初始值相差2个数量级,说明该相变为不可逆相变。结合第一性原理计算结果表明,柯铁矿结构更小的带隙是导致TiO2电阻率减小的根本原因。     

高压下锐钛矿TiO2的电阻率及能带结构的研究

应用在位电阻率测量方法研究高压下锐钛矿TiO2的电学性质. 通过研究电阻率随压力变化的异常变化点, 观察到了TiO2从锐钛矿-柯铁矿-斜锆石的相变. 卸压后,电阻率和初始值相差2个数量级, 说明该相变为不可逆相变. 结合第一性原理计算结果表明, 柯铁矿结构更小的带隙是导致TiO2电阻率减小的根本原因.     

Pressure dependence electrical resistivity in DVT grown molybdenum dichalcogenides

Abstract

Single crystals of MoS _x Se_2?x (x=0, 1, 2) have been grown by direct vapour transport method. Pressure-dependent d.c. electrical resistivity measurements have been carried out on the grown crystals to check the possibility of phase transition up to 8 GPa. However, no such transition is observed in the present case but a decrease in resistivity is found with increase in pressure. The observed results have been analysed and discussed on the basis of band structure.     

Spin disorder resistivity of spin glasses with application to AgMn

The impurity resistivity due to scattering from disordered spins is calculated for temperatures above the ordering temperature T₀. It varies linearly around T₀, but shows a maximum at higher temperatures, in agreement with experiment.     

A study of the temperature and pressure dependence of the electrical resistivity of a dilute Cr-Ge system

The electrical resistivity of a series of dilute Cr-Ge alloys containing up to 1.5 atm % Ge, was measured as a function of temperature and pressure. The measurements clearly demonstrate the existence of resistivity anomalies at the incommensurate-commensurate spin density wave transition temperature (T_IC) in contrast with recently reported results. The complete magnetic phase diagram, determined for the first time from electrical resistivity measurements, contains a triple point in contrast with previous neutron diffraction results but in agreement with thermal expansion measurements. It was found that the incommensurate spin density wave state is absent in alloys with more than 1 atm % Ge. The Néel temperatures and incommensurate-commensurate transition temperatures are affected differently by pressure. Pressure decreases T_N in all the alloys while it increases T_IC for those alloys in which the incommensurate-commensurate transition occurs. The decrease of T_N with pressure is much larger for the commensurate-paramagnetic than for the incommensurate-paramagnetic transition. The electrical resistivity of the alloys at room temperature behaves anomalously with applied pressure. This anomalous behaviour is attributed to an antiferromagnetic-paramagnetic phase transition that is induced in the alloys by applied pressure.     

On the electrical resistivity of spin glasses

The resistivity of spin glasses with momentum independent static susceptibility _k = due to the disorder of the spin system and to spin excitations is calculated to lowest order in the temperatureT, and above the freezing temperatureT _f . The diffusive modes proposed by Dzyaloshinskii and Volovik lead for to a resistivity of the form=AT ² –BT ^5/2 with positive coefficientsA andB. TheT ^3/2 contribution observed by Ford and Mydosh can be explained by the existence of ferromagnetic clusters. For, a classical theory with 1 for all excitation energies and with _k = leads to a constant resistivity (the Yosida limit). The observed increase of the resistivity aboveT _f can be explained by rather strong magnetic short range order.SFB 125 Aachen-Jülich-Köln     

Pressure dependence of the electrical resistivity and the ionization energy of Cr In n-type InP

The electrical resistance of chromium-doped, n-type InP has been found to increase exponentially with hydrostatic pressure (up to 4.7 kbar) at 273 K, 301 K, and 344 K. The resistivity activation energy increases by 6.5 × 10^-6 eV/bar. This rate equals the difference between the pressure dependences of the lowest conduction band minimum at $\text{k}$ = (000) and the <111> subsidiary minima determined by others. Our results indicate that pressure increases the ionization energy of a Cr donor level whose wave function has a large contribution from the <111> minima. It is suggested the Cr donor level is due to Cr⁺³ occupying an indium site.     

Temperature dependence of the electrical resistivity in amorphous metals

In amorphous metals the electrical resistivity increases linearly in the temperature range from 2 to 40 K. This result differs fundamentally from the nonlinear behaviour known for crystalline metals and it suggests the conduction electrons not to be scattered by the vibrations of the amorphous point lattice. The temperature dependent part of the resistivity in amorphous metals is explained with scattering of conduction electrons by fluctuations ofp-electrons.     

Lattice location of Mn in the spin glass CuMn

The lattice location of Mn in a Cu10 at.% Mn single crystal has been determined using ⁴He ion channeling and ion-induced X-rays. It is found that the Mn atoms are 100% in substitutional sites.     

The resistivity maximum in the ternary spin glass system Au-Cu-Mn

The temperature of the resistivity maximum, T_m, in the ternary spin glass system Au-Cu-Mn has been analysed in terms of Larsen's theory in order to highlight the contribution from the Kondo effect and the RKKY interaction energy to the resistivity maximum in spin glasses. The competition between these two contributions has been effectively illustrated and a good agreement with theory is obtained for samples with varying magnetic and nonmagnetic atom concentration. A comparison of the dependence of T_m and the RKKY interaction energy on the lattice pressure generated due to addition of Au with reported pressure studies on Mn alloys shows that there is a close relation between the lattice pressure and the externally applied pressure.     

Pressure dependence of the resistivity of zinc oxide

The change of resistivity of n-type ZnO with hydrostatic pressure has been found to be 2.2 × 10^?6/kg cm^?2 and is nearly linear for pressures up to 28000 kg/cm². This result can be shown to be incompatible with a simple model of electron mobility which assumes that the scattering due to acoustic modes arises from a deformation potential associated with lattice dilatation.     

On the electrical resistivity of noble based transition metal dilute alloys

We apply the CPA expression of the electrical conductivity to the case of Au-based alloys containing 3d and 4d transition impurities. In this approach, a s-diagonal disorder larger for the 3d case than for the 4d one can explain the measured differences in resistivity between these two cases.     

Pressure dependence of the resistivity of several amorphous alloys

Measurements under hydrostatic pressure of the electrical resistance of a series of metglas alloys and one alloy of NiY have been made in the range 0–5 kbar and 77–300 K. In general the behaviour fits no general pattern, except that Metglas 2204 (BeTiZr) obeys a simple prediction of the Ziman model as found by Nagel for thermopower.     

Pressure dependence of the magnetisation and Mn nmr of Mn4N

Abstract

The expanded lattice material Mn₄N contains two types of Mn site. The ⁵⁵Mn NMR at the Mn(I) site has been measured to 9 kbar at 77K. The Mn(I) NMR frequency, and the magnetisation, increased with pressure which is attributed to a decrease in the magnitude of the moment at the Mn(II) site.     

The temperature dependence of the electrical resistivity of granular metals

A simple percolation model of the hopping conduction in granular metals is proposed. The separation between the grains, in this model, is a random variable uncorrelated with the activation energy, the latter being dominated by the intragrain level splitting. The model is capable of reproducing the resistivity exp $\text{(}\text{T}{}_0\text{T}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ law over a wide temperature range, in spite of the narrow range of the grain diameters, explaining the recent observations of Choi et al.     

The temperature dependence of the electrical resistivity of gold films

An analysis is presented of resistivity data on thin gold films with a view to characterizing any surface-caused quadratic temperature dependence (T²) to the resistivity. No evidence is found for a T² term varying in magnitude according to the inverse sample thickness. This is in accord with other studies on gold foils and disagrees with a recent suggestion that surface scattering causes a T² contribution to the resistivity of the noble metals.     

Temperature dependence of the electrical resistivity of amorphous Pd-Si alloy

Czechoslovak Journal of Physics - The temperature dependence of the electrical resistivity of amorphous binary Pd-Si alloy has been calculated by means of the t-matrix formulation of the extended...     

Magnetic susceptibility and electrical resistivity of dilute liquid copper - iron alloys

Electrical resistivity and magnetic susceptibility measurements on dilute liquid CuFe alloys are reported. Small additions of Fe increase the resistivity of liquid Cu in a drastic manner, whereas the temperature coefficient is found to be decreased. Due to the localized magnetic moments of the impurity atoms the diamagnetism of Cu is converted into a strong temperature-dependent paramagnetism indicating about 3.5 unpaired d electrons per Fe atom. The electronic properties of CuFe resemble those of liquid CuMn and AuFe which, in the solid state, are known for their Kondo-like behaviour. The experimental findings are tentatively interpreted in terms of spin-disorder scattering with special emphasis on the negative temperature coefficient of the impurity resistivity.