Hall effect and negative magnetoresistance in thin crystals of NbSe

We have measured the Hall effect and the transverse magnetoresistance in NbSe3 single crystals. In the liquid helium temperature range we observed an absolute negative magnetoresistance (NMR) — the value of the resistance under magnetic field being much lower than that at zero field — in NbSe3 single crystals with a thickness less than 5 μm with the magnetic field oriented in the (b, c) plane. We show that this NMR effect is observed in the magnetic field range in which the Hall constant changes its sign. The results are qualitatively explained by the change of the surface scattering contribution to the magnetoconductance in the magnetic field range near the Hall voltage zero crossing