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0OPEN ORBITS AND TRANSPORT ANISOTROPY IN METALLIC LaB6
Anisimov M.1' 2, Voronov V.1, Samarin N.1, Bogach A.1, Krasnorussky V.2, Glushkov V.1, Demishev S. 1 2' 3, Shitsevalova N.4
1Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia,
E-mail: anisimov.m.a@gmail.com 2Vereshchagin Institute for High Pressure Physics of RAS, Troitsk, Russia 3National Research University 'Higher School of Economics', Moscow, Russia
4Frantsevich Institute for Problems of Materials Science NASU, Kyiv, Ukraine
Nonmagnetic LaB6 is the metal with extremely low work function ~ 2.66 eV), finding diverse applications in electronic devices as the most commonly used material for contact electrodes, electronic emitters, etc. At the same time LaB6 exhibits interesting physical properties in the basic aspect [1]. Recently a discussion about structural instability accompanied by possible formation of dynamic charge stripes in metallic members of RB12 and RB6 frame-clustered systems has been renewed in literature.
Here we present a detailed study of galvanomagnetic properties (electrical resistivity, transverse magnetoresistance) in high quality single crystals La(10Bx, 11Bi-x)6 with various boron isotopes (x = 0,
0.188. 0.25, 0.5, 0.75, 1). The measurements have been performed in experimental geometry I||[110], H||[100] at temperatures 2 - 300 K in magnetic fields up to 82 kOe.
Interesting effect (Fig. 1) was observed for LanatB6 sample with the lowest among other members of La(10Bx, 11B1-x)6 family residual resistivity p0 ~ 1.7 10-8 Q cm. In particular, (i) special singular points (SP) which are reproduced with the displacement at 180° were registered on angular dependences of transverse magnetoresistance (TMR) in fields above 20 kOe. The region of existence of SP (T < 40 K) corresponds to the closure of phonon channel of scattering with the transition to residual scattering regime. (/'/) SP appear in narrow interval of angles Acp ~ -1.8 -r- -23.4 near the direction H||[100] (Fig.1a). The effects (i)-(ii) may be related with the features of Fermi surface topology and especially with open orbits, which are expected for LaB6 [2]. This approach is confirmed by analyzing field dependences of positive TMR Ap/p = f(H) obtained at fixed position of the sample (Fig.1b). (iii) The change of the topology of electron trajectory from closed to open orbits leads to significant evolution of both the shape and the amplitude of TMR (almost at 10 times) from saturating behavior for the first case to unsaturated enhancement for the last one, similar to the results published in classical work [3].
References
1. Anisimov M., Samarin N., Bogach A., Azarevich A., Demishev S., Glushkov V., Shitsevalova N., Voronov V. // Sol. St. Sci. - 2020. - V. 103. - P. 106181.
2. Onuki Y., Umezawa A., Kwok W. K., Crabtree G. W., Nishihara M., Yamazaki T., Omi T., Komatsubara T. // Phys. Rev. B. - 1989. - V. 40. - P. 11195-11207.
3. Alekseevskii N. E., Gaidukov Yu. P. // Sov. Phys. JETP - 1960. - V. 37. - P. 481-484.
