Vortex lattice symmetry in hexagonal superconductor CaAlSi probed by small angle neutron scattering

First-Order Reorientation Transition of the Flux-Line Lattice in CaAlSi

“…3 is indicated by the solid line yielding an anisotropy, γ λ = 2.7(1). The value of γ λ is in excellent agreement with previous values of γ ξ determined from magnetic and transport measurements [7,8] and slightly larger than the value of 2 obtained by Kuroiwa et al [31] from SANS measurements.…”

“…1(a)-(d) show typical diffraction patterns from the FLL of CAS measured at 2 K in fields of (a) 97, (b) 185, (c) 250, and (d) 294 Oe applied parallel to the c axis. The only previous SANS measurements on 6H-CAS suggested that the FLL was not perfectly hexagonal [31]. In our measurements, a perfectly hexagonal lattice was found for all applied fields.…”

“…No further reorientations of the FLL were observed in applied fields of up to 2 kOe. An earlier SANS study of 6H-CAS found no evidence for a FLL reorientation as the measurements were not carried out in sufficiently low applied fields [31]. An H-T phase diagram of CAS is shown in Fig.…”