Joshi, Amish GKryukov, Sergiy A.De Long, Lance E.González Herrera, Elvira MaríaNavarro Palma, ElenaVillegas, Javier E.Vicent López, José Luis2023-06-202023-06-202007-05-010021-897910.1063/1.2714302https://hdl.handle.net/20.500.14352/52121© 2007 American Institute of Physics. Research at University of Kentucky supported by U.S. Department of Energy and Kentucky Science and Engineering Foundation. Research at Universidad Complutense supported by Spanish Ministerio de Educacion y Ciencia, Comunidad de Madrid y Santander-UCM. One of the authors (A.G.J.) was supported by an Indian Department of Science and Technology BOYSCAST Fellowship No. SR/BY/P-01/ 04.We report vibrating reed and superconducting quantum interference device magnetometer data that exhibit prominent dips or oscillations of the superconducting (SC) onset temperature, Delta T(C)(H)approximate to 0.01-0.7 K, for a [Nb(23 nm)/Ni(5 nm)](5) multilayer (ML) in dc magnetic fields applied nearly parallel to the ML plane. The vibrating reed data exhibit reproducible structures below T(C) that may reflect multiple SC transitions, but they are sensitive to ac field amplitude and dc field orientation. This striking behavior poses challenges for theoretical and experimental investigations of interfaces between SC and ferromagnetic layers that involve magnetic pair breaking effects, "pi phase shifts" of the SC order parameter, and exotic ("LOFF") pairing states. Alternatively, the anomalies may mark dynamical instabilities within a confined, strongly anisotropic Abrikosov vortex lattice.engjournal articlehttp://dx.doi.org/10.1063/1.2714302http://eprints.ucm.esopen access538.9SuperlatticesTransitionVorticesLatticesStateFieldFísica de materialesFísica del estado sólido2211 Física del Estado Sólido