Measurement of the low-field Hall coefficient by d.c. SQUID technique

Milnera

Koǒcer

et al. 2000

phys. stat. sol. (a)

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The method of electrical dislocation density measurement, which was successful in plastically deformed pure noble metals, is applied for the first time to dilute alloys, and the parameters for the electrical dislocation density measurement, i.e. the temperature dependence of the deviation from Matthiessen's rule and of the low-field Hall coefficient were investigated in Cu±Au alloys with 0.075 and 0.3 at% gold. The results for the dislocation density, which rely on the modelling of the true dislocation resistivity by means of the two-group model are especially satisfactory for the 0.075 at% alloy. Additionally the dislocation density was checked by X-ray Bragg profile analysis. The comparison of the latter method with the electrical method shows that small dislocation loops originating from the agglomeration of deformation induced vacancies are part of the total dislocation density.

Section: Methodsmentioning

confidence: 99%

The Deviation from Matthiessen's Rule and Electrical Dislocation Density Measurement in Dilute Cu-Au Alloys

Milnera

Koǒcer

et al. 2000

phys. stat. sol. (a)

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“…(7) and (8) agreed for one and the same sample within 0.1% although the mass loss after the final diffusion annealing was about 5% of the initial sample mass. The low-field Hall coefficient at 4.2 K of some selected samples was measured by a SQUID picovoltmeter (resolution 1.5 pV Hz --1/2 ) as described in [16] in order to have the true low-field limit [17,18]. For completeness the Hall coefficient at room temperature of several samples was measured by a standard Hall effect equipment at a field of 2 T. The quantities r 0 and a 0 are independent of the shape factor and could be measured with an accuracy better than 10 --3 (a 0 ) and 10 --4 (r 0 ).…”

Section: Methodsmentioning

confidence: 99%

The Deviation from Matthiessen's Rule at 4.2 K in Dilute Copper-Gold-Germanium Alloys

2001

phys. stat. sol. (a)

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Subject classification: 72.15.Eb; 72.15.Lh; S1.3The deviation from Matthiessen's rule (DMR) of dilute copper-gold-germanium alloys was measured at 4.2, 77 and 273 K. The low-field Hall coefficient of binary Cu-Au and Cu-Ge alloys was also measured at 4.2 K to determine anisotropy parameters for the explanation of the DMR in the ternary alloys. In order to control the shape factor of the ternary samples the germanium content was brought into binary Cu-Au samples by vapour deposition and diffusion annealing. The limitation of the usual two-group model for the investigated alloys is shown and a more accurate threegroup model is presented. Especially the DMR at 4.2 K of the ternary samples in the range 20-30 nW cm (as well as the DMR at 273 K) can be substantiated by the low-field Hall coefficient and by the anisotropy of scattering rates obtained from the de Haas-van Alphen effect for the binary alloys.

“…In order to have the low-field condition at 4.2 K ( W Z << 1, 6) cyclotron frequency, z mean relaxation time of the conduction electrons) we measured the Hall voltage of the single crystals at the magnetic induction B = 2 to 10 rnT and current 2.5 A using a dc-SQUID picovoltmeter described elsewhere [8]. Fig.…”

Section: Low-field Hall Effect Measurementsmentioning

confidence: 99%

Electrical dislocation resistivity and anisotropic scattering in high‐purity copper single crystals

Physica Status Solidi (b)

1996

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The experimental dislocation rcsistivity (or the deviation from Matthiessen's rule (DMR)) at 4.2 and 77 K of sevcral single slip and multislip crystals was investigated. Additionally low-field Hall effect nieasurernents at 4.2 K using a dc SQUID picovoltmeter were pcrformed in order to study the anisotropy of electron-dislocation and electron-impurity scattering directly. It is shown that, oxygen annealing applied to increase tiic "elcctrical purity" of the crystals does not change the character of the scattering behaviour. The anisotropy parameters Adis for electron-dislocation scattering derived within the two-group model are in good agreement with recent rcsults for high-purity polycrystals.