Penetration depth of YBa2Cu3O7 measured by polarised neutron reflectometry

Abstract We have applied the technique of polarised neutron reflectometry (PNR) to investigate the magnetic field profile near the surface of YBa 2 Cu 3 O 7 films at 4.3 K. The samples comprised 700–1400 nm of c -axis oriented, single crystal YBa 2 Cu 3 O 7 deposited by laser ablation on SrTiO 3 substrates. The measurements were carried out on the CRISP reflectometer at the ISIS facility. The PNR technique measures the magnetic induction profile perpendicular to the surface, and so in our case the decay of flux in the c -direction was measured with a field applied parallel to the ab plane. We present preliminary data for the polarised and unpolarised reflectivity