Alternating Current Electromagnet Type Hysteresis Loop Tracer for Minerals and Rocks

Abstract

Photomicrography may be readily accomplished by standard techniques. Exposure times for luminescent photography, using High Speed Ektachrome film, range from one-half second to about one minute. A cadmium sulphide cell ohm-meter combination has been used for estimating exposure times. Some light originating in the air discharge does reach the specimen; and for critical work and the best quality photography, this stray light can be largely removed by use of a gas other than air to support the discharge. This other gas may be admitted through the mechanical leak. Both hydrogen and helium are superior to air in this respect, but hydrogen works best. Using a hydrogen discharge at the optimum pressure, only a very dull red discharge can be observed in the lower region of the discharge tube. This allows only minimal light to reach the specimen. Even this minimal amount could effectively THE REVIEW OF SCIENTIFIC INSTRUMENTS be removed by incorporating an interference filter in the optical path.Although the instrument has been developed primarily for observation of geological specimens, it should prove useful for luminescent observations of other substances. Applications are likely to be found in such fields as ceramics, cements, synthetic crystal production, and particularly in the area of solid state physics research. ACKNOWLEDGMENTSThe author is indebted to Professor J. V. Smith who discussed freely the properties which a luminescence device should have, and in particular, very graciously relayed to the author the experience of Dr. J. V. P. Long who found that a simple, poor vacuum, alternating current device was feasible.A hysteresis loop tracer employing an alternating current electromagnet capable of providing fields up to 3600 Oe is described. Merits of the present system over other types of loop tracers are pointed out. Some typical hysteresis loops obtained using the apparatus are also presented.

Magnetic properties and domain state of the magnesium ferrite–magnesium titanate solid solutions

“…The variation of initial susceptibility with temperature and of Curie point (T,) were measured using the instruments described by Radhakrishnamurty and P. W. Sahasrabudhe [ 121. Hysteresis characteristics like magnetization (M,) coercivity (H,) were determined by an ac hysteresis loop tracer described in the literature [13]. Mossbauer spectra were recorded at room temperature with constant acceleration drive and multichannel analyser (MCA 38A, ECIL, India) [14].…”

Prefolding and overprint magnetic signatures in Precambrian (∼2.9–2.7 Ga) Igneous rocks from the Pilbara Craton and Hamersley Basin, NW Australia

“…Anisotropies of susceptibility were measured using Digico equipment, and ARUN Electronics equipment similar to that described by Likhite et al [1965] was used for measuring bulk hysteresis parameters. The Digico anisotropy delineator has been calibrated against a susceptibility bridge thus avoiding problems recently brought to light by Hrouda eta!.…”

“…A component of intermediate stability, however, is often seen directed to the southwest and down (Figure 13a). Although the resolution of these three components is sometimes poor, there is often a hint of the presence of the intermediate component reflected in the orthogonal plots which suggests that at least some of the components are CRM with overlapped stability spectra [McClelland Brown, 1982]. Figure 13b is a typical example of this behavior.…”

Paleomagnetism of diabase dikes from the Bonavista Bay area of northeastern central Newfoundland

“…Hysteresis loops were obtained using apparatus similar to the one described by Likhite et al (1965); representative curves are shown in Fig. 9d, both at -196OC (bottom trace) and at room temperature (top trace).…”