Anomalous Resistivity Behavior Research Articles

Seebeck coefficient of binary chromium alloys containing molybdenum or tungsten

The Seebeck coefficient (ifS) of Cr alloys containing 0.6, 3.2, 5.1, 6.9, 8.8 at.% Mo or 0.3, 0.7, 1.0, 3.4 at.% W has been measured as a function of temperature ( T) between 50 ° and 350 °K. The S vs. T curves show large anomalies (increases in S) in this temperature range due to the transition from the paramagnetic to the antiferromagnetic state, made up of transverse spin density waves incommensurable with the chromium lattice. In the paramagnetic region Cr-Mo alloys approximately obey the Nordheim-Gorter rule. The Cr-W alloys do not obey this relation because of the anomalous behavior of the electrical resistivity with respect to the composition in the paramagnetic state. The increase in S, due to the onset of the antiferromagnetic state, can be approximately correlated with the increase in the electrical resistivity in Cr-W alloys. The Cr-Mo solid solutions show more complicated behavior.

Anomalous behaviour of the electrical resistivity in the compound Ce 3Al 11

Electrical and magnetic properties are reported for intermetallic compounds (Ce 1− x La x ) 3Al 11 between 1.3 and 300°K. The occurrence of a minimum at about 20°K in the resistivity is attributed to the Kondo effect.

Local Atomic Arrangements in a Nickel—10 Atomic Percent Tungsten Alloy

The x-ray diffuse scattering from both single-crystal and polycrystalline samples of a Ni—10 at.% W alloy has been measured and interpreted to yield information about local atomic arrangements in the alloy as a function of heat treatment and cold deformation. The short-range-order parameters for a sample which had been quenched from 950°C agreed well with those computed from a model based on long-range-ordered Ni4W. The degree of short-range order gradually decreased as the alloy was cold worked, but could be recovered at annealing temperatures well below the recrystallization temperature. An attempt was made to use these results to explain the anomalous behavior of the electrical resistivity upon plastic deformation.

Anomalous Behavior of Electrical Resistivity in the Alloys with High Concentration of Magnetic Atoms

Anomalous Behavior of Electrical Resistivity in the Alloys with High Concentration of Magnetic Atoms

Resistance Anomaly in Palladium-Silver Alloys Containing Rare Earth Impurities

Electrical resistivities of Pd and three Pd–Ag alloys (Pd0.5Ag0.5, Pd0.35Ag0.65, and Pd0.25Ag0.75) containing small amounts of Gd and Nd have been determined at temperatures between 1.2° and 40°K. All lanthanidedoped alloys were observed to have resistance anomalies which were similar in character for the heavy and light rare earth solutes. However, the anomalies were found to vary drastically with the host lattice. With decreasing temperature, the resistivity-temperature curves show (1) a sudden increase in slope in the matrix of Pd, (2) a minimum in Pd0.5Ag0.5, and (3) a minimum and a maximum in Pd0.35Ag0.65 and Pd0.25Ag0.75. The present alloys, which constitute a continuous series of solid solutions having a common magnetic impurity, have thus exhibited a gradual shift from one to another of the three possible types of anomalous resistance behavior predicted for dilute magnetic alloys by Kondo and other workers. The shift signifies that a dominant role is played by the host lattice in the mechanism leading to a resistance anomaly. The difficulties in reconciling the present results with predictions on the Kondo theory as related to the sign of the effective s-f exchange integral and earlier EPR measurements are discussed.

Surface space-charge barriers on semiconducting barium titanate

The work function of semiconducting barium titanate has been monitored as a function of temperature with the aim of testing Heywang's theory of the anomalous resistance behaviour of the polycrystalline material. As the temperature is raised the resistivity transition is accompanied by an increase in the work function which is comparable in magnitude with the change in the height of the intergranular barriers deduced by Heywang. Above the transition temperature the work function decreases and does not remain constant as expected from the theory. There is also a very pronounced thermal hysteresis in the work function changes. These two effects are explained by the desorption of gas from the surface, activated by the changes in the surface space charge barrier.

Some Physical Properties of the and Phases in the U-Zr System

Electrical resistivity and magnetic susceptibility measurements are reported for U-70 and 74at.% Zr in both the γ and δ phases. Negative temperature coefficients of resistivity were found in the metastable γ phase of U-70at.% Zr, and also in the δ phase of both alloys between 90° and 870°K. The Pauli weak spin paramagnetism, exhibited by both specimens, always increased with temperature. The results support the view that the δ phase is primitive hexagonal and not an ordered form of the body-centred cubic γ phase. The anomalous resistivity behaviour may be a consequence of the band structure of the alloy.

The electrical resistivity and super-conductivity of some uranium alloys and compounds

The electrical resistivity and superconductivity of a series of a (orthorhombic) and quenched y (body-centered cubic) binary alloys of uranium with niobium and molybdenum were investigated at temperatures down to 1 °K. Anomalous resistivity behavior occurs in both types of structure. The γ-alloys are particularly unusual in possessing a negative temperature coefficient from room temperature down to the superconducting transition point. Both systems exhibit superconducting transitions, the γ-alloys in the vicinity of 2°K and the α-alloys closer to 1°K. Some success was achieved in a qualitative interpretation of the resistive and superconductive properties of the alloys in terms of a hypothetical band structure of uranium. Ten intermetallic compounds of uranium were also tested for superconductivity down to about 1°K. Four new superconductors were discovered: UCo (1.70°K), U 6Mn (2.32°K), U 6Fe (3.86°K) and U 6Co (2.29°K). The last three compounds are isomorphous and include the first superconducting compounds of manganese and iron.

The effect of addition elements on the electrical resistivity of α-titanium

As part of a study of the effect of alloying elements on the anomalous electrical resistivity of metallic titanium, resistivity measurements at temperatures up to about 800°C have been made on a series of solid solutions based on the hexagonal a modification of titanium. The addition elements, though limited in number and concentration range by the very restricted solubility of many elements in α-titanium and by difficulties in fabricating suitable specimens, have been selected to represent a series of different valencies, and one interstitial element, oxygen, has been included. The results have indicated that the metallic elements, from the point of view of their effect on the resistivity of α-titanium, can be grouped into two classes—transition metals and others. Oxygen differs from the nontransition metals only in its effect on the temperature at which the anomalous resistivity behavior begins. The significance of the results is discussed, and it is concluded that the findings cannot be finally interpreted until information on other electron-dependent properties of titanium alloys becomes available.