Magnetoresistance high-field

Figure 1.36. Magnetoresistance measurements performed between 9 and 12 T at 380 mK on two high-quality /9h-(BEDT-TTF)2I3 single crystals (a) and (b). In the inset in (a) the high-field magnetoresistance at 380 mK is shown on an enlarged scale versus (H represents B) and clearly reveals an enhanced anharmonicity at increased fields. The inset in (b) shows the inverse field values of 133 oscillation peaks vs. integral numbers. The almost perfect linearity is a test for both the origin of the oscillations and the quality of the data. The slope provides a fundamental field of 3730 T. Reprinted with permission from W. Kang, G. Montambaux, J. R. Cooper, D. Jerome, P. Batail and C. Lenoir, Physical Review Letters, 62, 2259 (1989). Copyright (1989) by the American Physical Society.

Fig. 17. Magnetotransport properties of a 200-nm thick film of Ga -x Mnr As with x = 0.0S3 at 50 m K in high magnetic fields, (a) Hall resistance, which is a linear function of the magnetic field in the high-field region (inset), (b) Sheet resistance negative magnetoresistance tends to saturate in the high-field region (Omiya et al. 2000).

Fig. 4. Magnetoresistance of Pn-(ET)2l3 between 9 and 12 T at 0.38 K, and 1/H plot of the peak positions versus integer numbers (left inset). The oscillations become strongly anharmonic at high fields (right inset).

If we count the number of valence electrons in a primitive cell, most of the lanthanide compounds are even in number, meaning that they are compensated metals. In this case the transverse magnetoresistance increases as /f" (I 2) for a general direction of the field. Note that the integer n is not equal to 2 because the high-field condition is not fully satisfied in the real compounds. When the magnetoresistance saturates for a particular field direction, often a symmetrical direction, there exist some open orbits whose directions are parallel to JxH, namely a=Ji/2 in -space. 

Figure 19 Mobility of carriers in P-rhombohedral boron obtained by different methods and different authors. 1, From space-charge limited currents 2 and 3, (1h 4, field effect 6, thermally activated hopping O, from electrical conductivity and spin density , (Xh. > from electrical conductivity and ESR magnetoresistance , from ESR line width +, band mobility A, hopping mobUity A, from photoconductivity V, from high-field conductivity, I, Hall mobility and photoconductivity. (See Ref. 2 and references therein.)...

Special applications, such as in high-magnetic fields, require special thermometers. The carbon-glass and strontium-titinate resistance thermometers have the least magnetoresistance effects. 

Song et al. [16] reported results relative to a four-point resistivity measurement on a large bundle of carbon nanotubes (60 um diameter and 350 tm in length between the two potential contacts). They explained their resistivity, magnetoresistance, and Hall effect results in terms of a conductor that could be modeled as a semimetal. Figures 4 (a) and (b) show the magnetic field dependence they observed on the high- and low-temperature MR, respectively. 

It is interesting to calculate the magnetoresistance in high magnetic field,... 

The Fermi surface of WC was proposed based on magnetoresistance and de Haas-van Alphen data taken under high magnetic fields at low temperatures. WC is a semimetal with equal numbers of electron and hole carriers of 1.5 X 1021/cm3. The Fermi surfaces consist of two electron pockets located at the point A and four hole pockets located at the point L, and at the point K or along the T A axis. These results indicate that the spin-orbit interaction is very important in WC. 

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