An upper bound for the magnetic force gradient in graphite

Abstract

Cervenka et al. have recently reported ferromagnetism along graphite steps. We present Magnetic Force microscopy (MFM) data showing that the signal along the steps is independent of an external magnetic field. Moreover, by combining Kelvin Probe Force Microscopy (KPFM) and MFM, we are able to separate the electrostatic and magnetic interactions along the steps obtaining an upper bound for the magnetic force gradient of about16 microN/m, a figure six times lower than the lowest theoretical bound reported by Cervenka et al. Our experiments suggest absence of MFM signal in graphite at room temperature.Comment: 14 pages, including supplemetary informatio