High-sensitivity vibrating reed studies of superconductors

Matching effects in the field and temperature dependences of the magnetization of superconducting/ferromagnetic Nb/Ni multilayers

“…This line of reasoning suggests that the matching anomalies evident in Figs. 2 and 3 may reflect subtle FLL rearrangements [22,23] that could be affected, or even driven, by Ni domain dynamics. …”

Magnetic instabilities along the superconducting phase boundary of Nb∕Ni multilayers

“…15,16 Magnetometry techniques offer alternative definitions of the SC onset, such as an initial diamagnetic change of the real part ͑mЈ͒ or an abrupt increase in the dissipative imaginary part ͑mЉ͒ of the ac magnetic moment in field-cooling ͑FC͒ experiments. 11 Vibrating reed ͑VR͒ magnetometry is particularly well suited for measurements of thin-film or anisotropic samples 17 and is essentially a transverse ac susceptibility technique that employs very low ac fields generated perpendicular to the dc applied field. 18,19 The high sensitivity of the VR to the entire sample bulk ͑which is not necessarily the case with resistivity measurements͒ at relatively low ac drives has been exploited to detect subtle transitions between equilibrium vortex lattice phases in bulk FM superconductors 17 and the onsets of plastic deformation and flow of the vortex lattice.…”

“…11 Vibrating reed ͑VR͒ magnetometry is particularly well suited for measurements of thin-film or anisotropic samples 17 and is essentially a transverse ac susceptibility technique that employs very low ac fields generated perpendicular to the dc applied field. 18,19 The high sensitivity of the VR to the entire sample bulk ͑which is not necessarily the case with resistivity measurements͒ at relatively low ac drives has been exploited to detect subtle transitions between equilibrium vortex lattice phases in bulk FM superconductors 17 and the onsets of plastic deformation and flow of the vortex lattice. The ͓Nb͑23 nm͒ /Ni͑5 nm͔͒ 5 ML was fabricated by dc magnetron sputtering on a Si ͑100͒ substrate and exhibited textured growth of Nb ͑110͒ and Ni ͑111͒ layers 3,4 with only small Nb-Ni interdiffusion and interface roughness.…”

“…17 The transducer was driven by a synthesizer tuned to the fundamental cantilever mode ͑frequency f = 650-865 Hz͒, and the reed amplitude was detected capacitively using a resonant rf ͑327 MHz͒ cavity technique. 17,20 The Si reed was oriented with its long dimension and the ML plane parallel to the dc magnetic field, which results in a transverse ac field ͑viewed in the moving VR frame͒ oriented perpendicular to the applied dc field. 18,19 Shifts of the VR frequency f ͑comparable to transverse mЈ͒ measure a magnetic restoring torque exerted on supercurrents that screen the ac field.…”

Peak effect in the superconducting mixed state of bulk Mo-Re alloys: a dc magnetization study

“…For example, in clean single crystals of various HTSC samples (Bi± Sr± Ca± Cu± O (Khaykovich et al 1996), Y± Ba± Cu± O (Deligiannis et al 1997) andNd± Ce± Cu± O (Giller et al 1997)), the PE is thought to be a signature of a second-order phase transition from the Bragg glass to vortex glass phase. The PE has also been a subject of much scrutiny in the intermediate valence C15 Laves phase superconductor CeRu 2 during the last 7 years (Roy 1992, Huxley et al 1993, Yagasaki et al 1993, Roy and Coles 1994, DeLong et al 1996, Kadowaki et al 1996, Dilley et al 1997. To date, there is still a debate about whether this PE in CeRu 2 arises owing to a dynamic crossover of pinning properties (DeLong et al 1996, Dilley et al 1997 or to a thermodynamic transition within the vortex matter .…”