The anisotropy of the activation energy of the flux pinning in a La1.85Sr0.15CuO4 single crystal was investigated by ultrasonic measurements in various directions of wave vector k, polarization vector u and magnetic fields H. The large activation energy of U(0 K, 14 T) = 972 K and small field dependence ∝H-0.3 were obtained for H ∥ c-plane, when the flux motion is parallel to the c-axis where the intrinsic pinning mechanism due to the layered structure is effective. The elastic modulus of the flux-line lattice which moves parallel to the c-axis is proportional to H2 cos 2θ, and the value of U rapidly decreases with increasing tilt angle θ between H and the c-plane (U(θ = 10°) ∼ 300 K, U(θ = 30°) ∼ 75 K). These angular dependences of the elastic modulus and the activation energy can be explained on the basis of the intrinsic pinning mechanism and the three-dimensional stepwise flux-line structure.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering