Electric field effect devices based on mesoscopic graphite are fabricated for
galvanomagnetic measurements. Strong modulation of magneto-resistance and Hall
resistance as a function of gate voltage is observed as sample thickness
approaches the screening length. Electric field dependent Landau level
formation is detected from Shubnikov de Haas oscillations in
magneto-resistance. The effective mass of electron and hole carriers has been
measured from the temperature dependant behavior of these oscillations.Comment: 4 pages, 4 figures included, submitted to Phys. Rev. Let