Non-Ohmic Out-of-Plane Transport in a High-Magnetic-Field-Induced Phase of Graphite

We have measured the longitudinal magnetoresistance ρ z z of graphite in high magnetic fields of up to ∼37 T at low temperatures down to ∼0.6 K. A dramatic increase in ρ z z was newly found in the high-field-low-temperature region. We have also found prominent non-ohmicity in the current-voltage characteristic in ρ z z over the relevant magnetic-field-temperature region. This non-ohmic behavior is reminiscent of sliding motion of a pinned charge-density wave or spin-density wave, the direction of which is mainly parallel to the c -axis. This magnetoresistance anomaly could be attributed to a magnetic-field-induced 2 k F -type instability due to the one-dimensionality caused by Landau quantization.