Magnetic flux rotation anomalies in superconducting La1.85Sr0.15CuO4

Vector magnetization measurements in La1.85Sr0.15CuO4 under fields slightly tilted from the crystallographic ab plane reveal flux rotation with distinctive behavior around T*approximate to 15 K. The temperature dependence of the onset-field H* for flux rotation and the dependence of H* upon the tilting angle are markedly different below and above T*, exhibiting pronounced anomalies in the crossover regime. Possible mechanisms for these anomalies, such as dimensional crossover in superconductivity or the anomalous behavior of the in-plane penetration depth due to coexistence of two superconducting gaps, are discussed.