Even harmonics of AC susceptibility in some sintered pellets of high temperature superconductors

Abstract

The real ( χ' _n ) and imaginary ( χ"_n ) parts of even harmonic susceptibility ( n ≤ 6) are measured as a function of external DC field ( H _dc ) in the field increasing ( H ↑) and decreasing ( H ↓ ) cycle. Hysteresis is observed between H ↑ and H ↓ cycles. In the H ↓ cycle, at a field, H _comp =4.2G, both χ' and χ" of all the even harmonics vanish indicating a true cancellation of fields in the intergrain region (H_eff ≈ 0) caused by the balance between H _dc and the remanent magnetization of the grains. The position of the extrema and the zero of the various harmonics undergo a shift proportional to the remanent magnetization of the grains at that particular field.