Magnetic Screening of NbN Multilayers Samples

Claire Z. Antoine (1) , Stéphane Berry (1) , Quentin Famery (1) , Julien Leclerc (1) , Jean-Claude Villegier (2) , G. Lamura (3) , A. Andreone (3)

1 DACM - Département des Accélérateurs, de Cryogénie et de Magnétisme (ex SACM)
2 SPSMS - UMR 9001 - Service de Physique Statistique, Magnétisme et Supraconductivité
3 CNR-SPIN-NA and Dipartimento di Scienze Fisiche

In 2006 Gurevich proposed to use nanoscale layers of superconducting materials with high values of Hc > Hc^Nb for magnetic shielding of bulk niobium to increase the breakdown magnetic field inside SC RF cavities [1]. We have deposited high quality "model" samples by magnetron sputtering on monocrystalline sapphire substrates. A 250 nm layer of niobium figures the bulk Nb. It was coated with a single and multi-stacks of NbN layers (25 or12 nm) separated by 15 nm MgO barriers, and characterized by X-Ray reflectivity and DC transport measurements. DC or AC measurement of HC1 is an important goal for multilayer evaluation during the sample evaluation phase. A clear increase of HC1 at low frequency is promising indication since HC1 is expected to increase with frequency (see e.g. [2] and references therein). We have measured the first penetration field (HP~HC1) on DC magnetization curves in a SQUID system. HP of NbN covered sample is increased compared to Nb alone. We have also developed a set-up that allows measuring a large range of field and temperature with a local probe method based on 3rd harmonic analysis. We have confirmed the screening behavior of a single 25 nm NbN layer placed on the top of a Nb Layer.

Domaines: Supraconductivité [cond-mat.supr-con]; Electromagnétisme; Instrumentations et Détecteurs [physics.ins-det]

Claire Z. Antoine, Stéphane Berry, Quentin Famery, Julien Leclerc, Jean-Claude Villegier, et al.. Magnetic Screening of NbN Multilayers Samples. 15th International Conference on RF Superconductivity (SRF 2011), Jul 2011, Chicago, Illinois, United States. ⟨hal-00651273⟩