Complicated shape of the superconductive transition curve revealed by a sensitive OFC-magnetometer

Abstract

Because of pick-up coil's flat design, relatively low operation frequency ( 23 MHz) and high relative resolution (10 6 ) a single-layer Open-Flat Coil-based tunnel diode oscillator (OFCmagnetometer) has advantages, compared to other test methods. They become crucial at nondestructive studies with thin flat HTS materials (with small signals), especially near (at start of the 'Cooper' pairs' formation). Due to these a new 'Para-Magnetic' peculiarity of the normal-to-superconductive (N/S) transition was detected recently in YBaCuO films. It precedes the 'Meissner' ejection and specifies details of an actually complicated shape of the N/S transition curve. We discuss influence of the currents and magnetic field on the PM effect and relationship between the quality of HTS material and amplitude of the effect. Differences between PM effect and externally close 'paramagnetic Meissner' and resistive 'peak' effects are discussed too.Index Terms-Fluctuation region, highsuperconductive (HTS) films, OFC-magnetometer, para-magnetic effect.