Fermi surface measurements magnetoresistance

The Fermi surfaces of these salts have been studied by measuring the quantum oscillations [183] such as SdH (Shubnikov-de Haas) and dHvA and geometrical oscillations (AMRO, angle-dependent magnetoresistance oscillation) ([4], Appendix, pp 445 48). The Fermi surface of k-(ET)2Cu(NCS)2 (Fig. 14c) calculated based on the crystal structure is in good agreement with those observed data [225]. 

The transverse magnetoresistance measurements on a Type A sample showed a saturation at around 10 Tesla, and a decrease up to about 20 Tesla [34]. SdH oscillations are superposed on this background magnetoresistance above 20 Tesla (Fig. 21). The oscillation period is 0.0015 T-i. The band calculation, based on the extended Hiickel MO, shows that the Fermi surface of this salt is composed of 2D closed (hole like) and ID surfaces (Fig. 9) [23]. The area of the extremal orbit calculated from the SdH oscillation (16.5% of the first Brillouin zone) is comparable to that of the closed Fermi surface in Fig. 9 (19%). More precise measurements on the magnetoresistance and other properties are underway. 

The Yb metal was the first rare earth metal studied with the de Haas-van Alphen measurement. Tanuma et al. (1967) purified a piece of raw metal by the vacuum distillation method. A single crystal specimen was obtained by spark cutting a large grain in a vapor condensed ingot. The resistivity ratio of the specimen was not reported. The crystal structure was determined to be fee by X-ray analysis at room temperature. Two de Haas-van Alphen frequencies were observed, and the authors suggested that they came from two separate pieces of Fermi surface. Datars and Tanuma (1968) deduced from magnetoresistance measurements at 1.3 K with fields up to 20 KG that there were no open orbits in Yb. Therefore, they concluded that Yb is semimetallic with two small, closed pieces of Fermi surface. ... 

The magnetization or the magnetic susceptibility is the most common one of these physical quantities, and its periodic variation is called the de Haas-van Alphen (dHvA) effect (de Haas and van Alphen 1930, 1932). It provides one of the best tools for the investigation of Fermi surface properties such as the extremal cross-sectional area S, the cyclotron mass w and the scattering lifetime x of metals (Shoenberg 1984). Sometimes other physical quantities are also measured for example, torque, static strain, ultrasonic velocity, and magnetoresistance, etc. The last type of measurement is called the Shubnikov-de Haas effect. 

Magnetoresistance measurements were done for RBg. Reflecting the multiply connected Fermi surface, open orbits were observed for LaBg, PrBg and NdBe (Onuki et al. 1989d). 

The recent Fermi surface study for Laln3 presents a sUghtly different picture (Umehara et al. 1991a) of the Fermi surface. That study concludes from their magnetoresistance measurements that there is no saturation with the implication that the open orbits arising from bridging of the hole surface from F to R (and also X) are not present in Lainj. This is not consistent with the band calculations... 

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