Anisotropy in Bi2212 single crystals studied by non-resonant microwave absorption: hysteresis and line shapes

Abstract

Microwave absorption in a high quality Bi2212 single crystal is studied at 77 K, using non-resonant microwave absorption (NMA) technique. NMA line shape and low field hysteresis are highly anisotropic. Two peaks, a narrow P 1-peak followed by a broad P 2-peak are observed for applied field perpendicular to the ab-plane. For the applied field parallel to the ab-plane, the broad P 2-peak disappears. For an intermediate orientation of the field, say ∼55°, to the ab-plane, the P 1-like peak broadens considerably with a possible mixing of both P 1-peak and P 2-peak. While there is a pronounced hysteresis in the P 1-peak just near zero field for applied field parallel to the ab-plane (Cu–O plane), this hysteresis in P 1-peak is nearly absent when the field is applied perpendicular to the ab-plane. In both these orientations, hysteresis is absent in NMA signals beyond the P 1-peak till very high fields. At the intermediate orientation angle of ∼55° to the ab-plane, the reverse sweep NMA signal collapses into the zero-base line. This is a remarkable hysteresis effect. This may be due to the interaction between Josephson vortices and Abrikosov vortices which can happen in tilted magnetic fields.