Galvanomagnetic Effects in Iron Whiskers

Abstract

Measurements have been made of the temperature dependence of the Hall effect in the range 1-300°K, and of the transverse and longitudinal magnetoresistance at low temperatures, in [100] and [111] iron whiskers of high purity (resistance ratios extrapolated to B = 0 ranged from 242 to 852). Analysis of the Hall data shows that both the "ordinary" Hall coefficient Ro and the "extraordinary" Hall coefficient R s vary enormously with temperature, and these variations cannot be explained by existing theories. The theoretical relation R s oc p 2 , where p is the resistivity, does not hold for temperatures below that of liquid nitrogen, and around this temperature Ro, which is positive at room temperature (hole conduction), becomes negative. Ro and R s appear to be isotropic, but at low temperatures these coefficients are extremely sensitive to impurities. The longitudinal magnetoresistance at 4.2 °K shows a large effect of the domain structure on the electrical resistance, which decreases appreciably (46% for the purest specimen) on magnetizing the specimens to saturation. Small negative magnetoresistance (^10%) has also been observed for some specimens in weak transverse fields.

Anomalous Hall effect in Fe (001) epitaxial thin films over a wide range in conductivity

“…23 Apparently, some dependence R O ͑ xx ͒ has been reported in polycrystalline Fe with different impurity contents. 26 The dependence of R O with temperature has also been reported in Fe polycrystals 26 and whiskers, 27 and may be understood within a simple multiband model. Nevertheless, it is important to note that we are calculating R O from the high-field slope of xy versus the applied magnetic field.…”

Proper Scaling of the Anomalous Hall Effect

“…[15,16], we used b ′ ρ 2 xx to fit the data in Fig. 1(d), but found the significant deviation when the Fe films were thinner than 6.5 nm, as clearly seen by the dashed lines in the figure.…”

“…In general, ρ ah could exhibit four types of behavior: (a) bρ 2 xx (e.g. Fe) [15][16][17][18], (b) aρ xx + bρ 2 xx (e.g. Co) [19,20], (c) bρ α xx (e.g.…”

The crystal structure determinations of OP(OCH2)3CCH3 and a hydrolysis product of PO3C6H9

“…Keeping these ideas in mind, R. Pivaz (I967) has suggested that the peculiar temperature variation of R^ which was observed by Dheer (1967) below liquid nitrogen temperatures may be due to an accidental degeneracy in the bands which occurs near the Fermi level and moves across it as the temperature Is As the bands move down still further, the electron ball will increase in size and become attached to the central electron octahedron, forming the original electron jack in the tungsten-like surface of Wakoh and Yamshita (1966) as shown in …”

“…The boat was covered by a single half cylinder but without end caps; this allowed the free flow of hydrogen gas. This vessel was then inserted ^This apparatus was set up and most of the crystals grown by Dheer (1967), into a quartz tube which in turn was placed in a split furnace and heated to 76o°C, and hydrogen gas was passed through at a rate of about 300 ml per minute. The iron was deposited on the walls of the iron vessel in the form of whiskers which varied in size up to 3cm in length and up to 0.5mm in thickness (in fact, a few whiskers grew as thick as 2mm, but these were of poor quality).…”