Activation measurements of the fractional quantum hall effect in a tilted magnetic field as a function of electron density

Tilted magnetic field activation measurements have been made at the 5 3, 4 3 and 7 5 filling factors. Measurements are presented as a function of carrier density. At these filling factors the magnetic field dependence of the gap is obtained. At both 4 3 and 7 5 filling factors a strong density dependence to the behaviour is observed. \ua9 1991.Peer reviewed: YesNRC publication: Ye