Addendum: ‘‘Reverse-field reciprocity for conducting specimens in magnetic fields’’ [J. Appl. Phys. <b>6</b>
                  <b>1</b>, 1079 (1987)]

Sample, H. H.; Bruno, William; Sample, Steven B.; Sichel, E. K.

doi:10.1063/1.339155

Cited by 9 publications

(12 citation statements)

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“…The presence of such a bias field violates the Reciprocity Theorem unless the sign of the magnetic field is switched between the two measurements [17], which can be exploited to measure the Hall coefficient in the presence of variations that would otherwise hide it. In the presence of a bias magnetic flux density B, the constitutive equation of an otherwise isotropic conductor becomes anisotropic E = J/ı -R H JuB, where E is the electric field and J is the electric current density.…”

Section: Hall Coefficient Measurementmentioning

confidence: 99%

Hall coefficient measurement for nondestructive materials characterization

Nagy¹

2013

AIP Conference Proceedings

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Articles you may be interested inNondestructive thermoelectric evaluation of the grit blasting induced effects in metallic biomaterials AIP Conf. Proc. 1511, 1504 (2013); 10.1063/1.4789220 Development of nondestructive non-contact acousto-thermal evaluation technique for damage detection in materials Rev. Sci. Instrum. 83, 095103 (2012); 10.1063/1.4749245Characterization of an epoxy bonded aluminum alloy sample applying dynamic acousto elastic testing AIP Conf.ABSTRACT. Although Hall detectors are widely used for magnetic flux density measurements in numerous electromagnetic NDE applications, measurement of the Hall coefficient of metals and their alloys for NDE purposes has not been successfully attempted before. While other intrinsic electric properties, such as electric conductivity and, to a lesser degree, thermoelectric power, are widely used for NDE, Hall coefficient measurements have never been really considered mainly because the measurements are rather difficult to carry out, especially in high-conductivity materials. In contrast to electric conductivity, the Hall coefficient is influenced mainly by the concentration density of the free charge carriers, i.e., electrons in metals, and not so much by their mobility, therefore it could be a valuable addition to our NDE arsenal. We modified the alternating current potential drop (ACPD) method with square-electrode configuration by adding an external bias magnetic field modulation to measure the Hall coefficient. The presence of such a bias field violates the Reciprocity Theorem unless the sign of the magnetic field is switched between the two measurements, which can be exploited to measure the Hall coefficient in the presence of other variations that would otherwise hide it. This new experimental method was tested on paramagnetic alloys and yielded a ±4% reproducibility that probably could be further improved by additional development efforts. As a first step towards illustrating some of the potential applications of this new technique, we have done reversible applied stress measurements in Al 1100 plates and found the sensitivity of the technique to elastic strain surprisingly high.

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Section: Hall Coefficient Measurementmentioning

confidence: 99%

Hall coefficient measurement for nondestructive materials characterization

Nagy¹

2013

AIP Conference Proceedings

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“…[63][64][65] Without an applied magnetic eld, interchanging the voltage and current contacts leads to the same measured resistance (known as reciprocity); however, in an applied magnetic eld this is only true if the magnetic eld is reversed (known as reverse eld reciprocity).…”

Section: Charge Carrier Concentration and Mobilitymentioning

confidence: 99%

“…Combining Hall effect measurements with van der Pauw resistivity reduces this problem and allows a simpler setup with 4 contacts instead of the 5 and 6-point geometries. 18,54,55 In addition, the van der Pauw conguration can be used to avoid the need for switching the magnetic eld [63][64][65][66][67] (see below).…”

Section: Charge Carrier Concentration and Mobilitymentioning

confidence: 99%

Measuring thermoelectric transport properties of materials

Borup

Boor

Wang

et al. 2015

Energy Environ. Sci.

314

256

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In this review we discuss considerations regarding the common techniques used for measuring thermoelectric transport properties necessary for calculating the thermoelectric figure of merit, zT.Advice for improving the data quality in Seebeck coefficient, electrical resistivity, and thermal conductivity (from flash diffusivity and heat capacity) measurements are given together with methods for identifying possible erroneous data. Measurement of the Hall coefficient and calculation of the charge carrier concentration and mobility is also included due to its importance for understanding materials. It is not intended to be a complete record or comparison of all the different techniques employed in thermoelectrics. Rather, by providing an overview of common techniques and their inherent difficulties it is an aid to new researchers or students in the field. The focus is mainly on high temperature measurements but low temperature techniques are also briefly discussed. Measurement guide for authors and reviewersMeasurements should always be repeatable on the same sample, and on new samples produced in the manner described. Thermoelectric effects are steady-state effects so any time dependence or hysteresis is indication that phenomena outside thermoelectric effects are at play. Materials with chemical oxidants/ reductants incorporated are likely to contain unstable internal voltages not due to thermoelectric effects. Unconventional samples or measurement methods deserve reexamination of assumptions. AccuracyTrue accuracy is not represented by a single heating curve from one sample, even with error bars representing instrument precision. Showing heating and cooling data and multiple samples gives a better indication of measurement variability for a typical type of sample. Anisotropy, cracks and inhomogeneities can lead to large variation in measurements. One unusual data point or sample outside the trend, particularly at temperatures just prior to decomposition, usually indicates a problem in sample or measurement. Unusual resultsTypical thermoelectric materials behave like heavily doped semiconductors with thermopower (absolute value of Seebeck coefficient) of less than 300 mV K À1 , resistivity of 0.1-10 mU cm, and are optimized when electronic contribution to the thermal conductivity is about 1/2 the total thermal conductivity. Extraordinary results should be checked by extra means. Unusual results can be caused by bad contacts, thermocouples that have broken, chemically reacted, or simply dried out of calibration. Exceptional resultsReported values of zT > 1 or in unexpected materials receive extra attention from reviewers who may ask for additional conrmation. Convincing measurements may need to be performed on the same sample along the same direction and be repeatable with other samples and measurement methods. There is no official record keeping for claimed or veried zT values. Several papers, patents and press releases have claimed extraordinarily high zT but most have been forgotten over time and likely resul...

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“…Experimental measurements of longitudinal magnetoresistance R xx in semiconductor quantum wells (QWs) can show asymmetry with respect to positive and negative magnetic field B. At large fields and low temperatures in the quantum Hall (QH) regime, larger R xx peaks appear for one sign of magnetic field, and smaller or vanishing R xx peaks for the opposite field [1] obeying the Onsager-Casimir relations [2][3][4]. However, the underlying cause of the asymmetries remained unknown until more recent work by Pan et al [5] in the fractional QH regime, whereby quantized R xx maxima were explained by assuming an electron density difference across the sample.…”

mentioning

confidence: 99%