Aharonov-Bohm oscillation in rings with permalloy

Aharonov-Bohm (A-B) rings with and without an inserted permalloy rod were f abricated from an AlGaAs/GaAs two dimensional electron gas (2DEG) wafer. Th e permalloy was a soft ferromagnetic alloy metal with a relative permeabili ty A of about 10(4). so that the effective susceptibility, including the de magnetizing effect, could be calculated from only the diameter and height o f the permalloy rod. Magnetoresistance of the A-B rings with and without th e permalloy rod was measured at T = 0.3 K using an external magnetic field. The magnetoresistance had oscillations of different periods in the two cas es. The main oscillation periods of the rings with and without the permallo y rod were 7.5 Oe and 28 Oe. respectively. clearly indicating that the perm alloy rod reduced the oscillation period. The reduction factor (26%) was co nsistent with the demagnetizing effect of the permalloy rod. If the permall oy rod is designed to be free of the demagnetizing effect, the reduction fa ctor should reach the order of the reciprocal of relative permeability mu.