Magnetization of symmetric 0-π Josephson junctions

Abstract

The magnetization curves and their corresponding phase, field, and current-density profiles for symmetric 0-π Josephson junctions (JJ’s) with length 2L are calculated from the sine-Gordon equation. The results show that there is a remanent magnetization Mr after switching off the field and a coercive field Hc which is required for magnetization reversal. With increasing l (≡L/λJ, λJ being the Josephson penetration depth), Mr increases from 0 to a value corresponding to Φ0/2 flux within the junction; and Hc increases from 0 and is proportional to the tunneling current density J0 and √J0 at l<0.7 and >6, respectively. Field-cooled magnetization MFC is paramagnetic if the flux in the JJ produced by the applied field H is less than Φ0/2. The hysteresis loop of very long (l>13) 0-π JJ’s is, similar to that of 0 JJ’s, of a surface-barrier type; for shorter (l<2.378) JJ’s, it is of anti-surface-barrier type. The magnetization of 0-π JJ’s can be explained by the coexistence of Φ0 vortices, whose entry and exit are through the edges, and Φ0/2 vortex, which is created at the center.

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