Transient and magnetic hysteresis in the microwave second-order response of BKBO crystals in the critical state

The second-order microwave response of Ba0.6K0.4BiO3 crystals in the critical state is investigated. Two different effects have been highlighted in second harmonic emission by superconductors exposed to intense pulsed microwave fields: a hysteretic behaviour and a time decay of the second harmonic signal intensity. Evidence is given that the two effects are strictly related.