Nonlinear microwave absorption in Ba1-xKxBiO3

Abstract

Nonlinear, field-modulated, direct microwave absorption (FMMA) was observed in copper-free Ba1-xKxBiO3 powder samples. The high-field, low-temperature results were compared to previous measurements of YBa CuO and BiSrCaCuO. The microwave wave determined critical field μ0H* = 0.7 μT and depinning current density J* c ≈ 1 × 107 A/m2 were obtained from the "Portis" model of flux pinning and depinning. These values were lower than the values obtained previously for YBaCuO and BiSrCaCuO as anticipated for a material with larger coherence length and comparable London penetration depth. A previously unobserved asymmetry of the FMMA in the field scan direction was also noted. © 1994.