We have measured the electrical resistivity, magnetoresistance, and Hall effect on several new single crystal samples and one polycrystalline sample of α-U. The residual resistivity ratios of these samples vary from 13 to 315. Matthiessen's law appears to hold above the onset of the charge density wave phase transitions that begin near 43 K, but not below this temperature. Sharp features at all three charge density wave transitions are observed and the effects of high magnetic fields on them are presented and discussed. The magnetoresistance is anisotropic, reaches 1000% at 2 K and 18 T, and does not exhibit Kohler scaling. The Hall coefficient is positive, independent of magnetic field, and slightly temperature dependent above about 40 K in agreement with earlier studies. Below 40 K the Hall coefficient changes sign as the temperature falls, varies with field, and becomes much more strongly negative at the lowest temperatures than has been reported. Some of our results suggest that a spin density wave may coexist with the charge density wave states. Superconductivity is observed in two of
The recently developed X-ray microbeam technique has been applied to the study of polycrystalline metals deformed by rolling. In this way it is possible to obtain information both about the mode of deformation of the material and about the nature of the cold worked state. Similarities in the behaviour of soft and hard metals are found and the results are discussed in terms of current theories of metallic strength.This paper contains only the results of the investigations of typical hard metals, copper, nickel and iron. It is found that a limiting particle size is reached when these metals are heavily rolled, and that the particles are distorted.
Man-made telluric micropulsaiions in the frequency range 0.001 2 Hz to 0.12 I i z have been invesiigaied near Montreal, Canada. Distinct telluric signals caused by electric-train activity have been identified and compared with the associated magnetic effects. The results indicate that some electromagnetic dist~lrbances of this kind may be more easily detected and identified by telluric means than by magnetic means. INTRODUCTION &Ian-made micropulsations have frequently been discussed in the literature, and the topic has recently been considered in papers by Lolclien and Shand (1964), andFraser andEllyett (1964). One reason for attempting to identify man-made micropulsations is to distinguish them from natural magnetic phenomena, a n important step in deternlining the origin and inode of propagation of the latter. Another reason is to facilitate the investigation of the propagation of lo\\--frequency electron~agnetic energy near a known source.Man-made inicropulsations have generally been detected by recording the magnetic-field variations. I-Io~vever, recordings a t WIont St. Milaire, near Montreal, Canada, have sho\vn the presence of strong telluric sigilals of manmade origin accompanied by a \veal; magnetic counterpart. As a result, telluric recordings \\?ere used to investigate the phenomenon. hIE.\SURISG E Q U I P M E S T Fixed Station at llfont St. HilaireThe magnetic micropulsation system I\ as designed and built by Pacific Naval Laboratory, Esquimalt, British Columbia. I t consists of pmetal cored coils feeding through 60-cycle rejection filters to chopper-stabilized amplifiers. The signals are then recorded on inagnetic tape and monitored n it11 chart recorders. Three coinponents with a sensitivity (at maximum gain) of 1.2'7 y/V output (at 0.01 Hz) were recorded in the passband 0.001 5-0.10 Hz.The telluric system includes three components (diamond-drill holes 400 ft. and 900 ft. deep being used for the vertical component) with a maximum sensitivity of 20 pV/V in the passband 0.001 2-0.12 Hz. Lead plates are used for surface electrodes, and lead pipe for electrodes in the drill holes. The outputs go to the same tape systein as the inicropulsation signals and are also monitored with chart recorders. ilfobile StationThis consisted of tivo telluric aillplifiers (identical ~v i t h those of the AIont St. Hilaire station) feeding into a tape system and monitored on chart records. Copper sulphate porous pots \yere used for electrodes.
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