Harmonic generation effect in high-Tc films

Harmonic generation in thick BPSCCO and thin YBCO films are reported. The application of an ac field (Hac > Hc1) of frequency f causes the generation of odd harmonics of frequency (2n+1)f. The application of dc field in addition to the ac field causes the appearance of even harmonics also in the BPSCCO film. However, the appearance of even harmonics is not observed in YBCO film with high Jc ∼ 1.6x106 A/cm2 and appearance of second harmonic with small magnitude is observed in YBCO film with low Jc ∼ 2x103 A/cm2. The variation of amplitudes of these harmonics are studied as a function of magnitude of ac and dc field and the results are explained in the framework of critical state model. A high-Tc film magnetometer based on the measurement of the amplitude of second harmonic has been developed whose field sensitivity is ∼ 1.5x10-8T. (author)