Experimental evidence of the lock-in transition of vortices in La 1.85Sr 0.85CuO 4 single crystal by SQUID measurements

Abstract

Using a double squid magnetometer, the angular variations of transverse ( M X ) and longitudinal ( M Z ) components of the magnetization of a La 1.85Sr 0.15CuO 4 single crystal has been investigated as a function of field at temperatures as close as possible to the critical temperature of this sample. To our knowledge, the lock-in transition in this system has not been yet formally observed experimentally by SQUID rotational magnetization measurements until now. Basing ourselves on the model proposed by Feinberg and Ettouhami, we confirm by different ways the existence of this transition by such measurements as well in the quasi-2D regime as in the quasi-3D regime. The signature of the lock-in transition has been also identified in the irreversible part of the magnetization.