Trace element content and magnetic properties of commercial HOPG samples studied by ion beam microscopy and SQUID magnetometry

In this study, the impurity concentration and magnetic response of nine highly oriented pyrolytic graphite (HOPG) samples with different grades and from different providers were determined using ion beam microscopy and SQUID magnetometry. Apart from sideface contaminations in the as-received state, bulk contamination of the samples in most cases consists of disk-shaped micron-sized particles made of Ti and V with an additional Fe contamination around the grain perimeter. The saturation magnetization typically increases with Fe concentration, however, there is no simple correlation between Fe content and magnetic moment. The saturation magnetization of one, respectively six, out of nine samples clearly exceeds the maximum contribution from pure Fe or Fe3C. For most samples the temperature dependence of the remanence decreases linearly with T - a dependence found previously for defect-induced magnetism (DIM) in HOPG. We conclude that apart from magnetic impurities, additional contribution to the ferromagnetic magnetization exists in pristine HOPG in agreement with previous studies. A comparative study between the results of ion beam microscopy and the commonly used EDX analysis shows clearly that EDX is not a reliable method for quantitative trace elemental analysis in graphite, clarifying weaknesses and discrepancies in the element concentrations given in the recent literature.Comment: submitted to Carbo

Master of Arts

thesisThe kangaroo rats (genus Dipodomys) belong to the order Rodentia and to the family Heteromyidae. Phylogenetically they are closely allied to the family Geomyidae, characterized in Utah by the common pocket gopher (genus Thomomys). The family Heteromyidae is represented, in Utah, by two other genera, namely: Perognathus and Microdipodops. The former is known, vernacularly, as the pocket mouse and the latter as the kangaroo mouse. All Utah Heteromyids are characterized by exceptionally large auditory bullae, grooved upper incisors, and fur lined cheek pouches

The distribution and taxonomy of Kangaroo rats (genus dipodomys) of Utah

journal articleThe first comprehensive work on the mammals of Utah was published by Barnes in 1922. In this work (Barnes 1922:86-87) only two kangaroo rats were known from the confines of the state. They were known at that time as Perodipus montcmus utahensis and Perodipus longipes. In Barnes revised edition (1927:107-108) these same two forms were still the only ones recognized for the state. They were now named Dipodomys ordii utahensis and Dipodomys ordii longipes. Grinnell (1919:203) had synonymized perodipus under the older name Dipodomys. Goldman (1917:109) placed these two Utah forms under Dipodomys ordii