  The capacitance of MgO based magnetic tunnel junctions (MTJs) has been
observed to be magnetic field dependent. We propose an equivalent circuit for
the MTJs with a parallel-leaky capacitance (Cl) across the series combination
of geometric and interfacial capacitance. The analysis of junctions with
different tunneling magnetoresistance values suggests higher Cl for low TMR
junctions. Using Cole-Cole plots the capacitive nature of MTJs is manifested.
Fitting with Maxwell-Wagner capacitance model validates the RC parallel network
model for MTJs and the extracted field dependent parameters match with the
experimental values.
