Indian Journal of Pure and Applied Physics

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Anomalous Critical Field Dependence of Cr-Nb-Cr Trilayers on Niobium Thickness


Affiliations
1 Materials Science Group, Indira Gandhi Center for AtomicResearch (IGCAR), HBNI, Kalpakkam -603 102, India
2 UGC-DAE Consortium for Scientific Research (CSR) Kalpakkam Node, Kokilamedu,Tamil Nadu -603 104, India

Cr-Nb-Cr trilayer thin films were deposited using DC/RF sputtering with Cr layer thickness maintained at 7.5 nm and Nb thickness varying from 30 nm to 229 nm, in order to study the interplay of antiferromagnetism and superconductivity. Various viewpoints have been expressed in the literature with respect to analyzing the anomalous properties that have been identified in superconductor/magnetic thin films. The study of Cr-Nb-Cr thin films were taken up to identify the existence of similar anomalous superconducting properties on account of antiferromagnetic-superconductor interfaces. X-ray reflectivity measurements showed high quality of thin film structure with minimum surface and interface roughness. Transport measurements down to 2K were carried out in the presence of magnetic fields up to 2 T applied perpendicular to the trilayers to deduce Tc. The suppression of Tc due to Cr layer is larger than proximity effect of similar metal films. It could be explained by proximity effect using antiferromagnetic Cr layer. Upper critical field measurements show a distinct non monotonic dependence of upper critical magnetic field and the slope on Nb layer thickness. The analysis due to WHH theory to deduce upper critical fields for the trilayer thin films studied did not match with experimental values. Although studies performed on Cr-Nb-Cr trilayers did not show any anomaly in Tc, it clearly showed a depression of Tc much larger than proximity effect, non monotonic behavior in Bc2(0) and dBc2/dTc behavior with Nb layer thickness.
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  • Anomalous Critical Field Dependence of Cr-Nb-Cr Trilayers on Niobium Thickness

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Authors

R Baskaran
Materials Science Group, Indira Gandhi Center for AtomicResearch (IGCAR), HBNI, Kalpakkam -603 102, India
L S Vaidhyanathan
Materials Science Group, Indira Gandhi Center for AtomicResearch (IGCAR), HBNI, Kalpakkam -603 102, India
D K Baisnab
Materials Science Group, Indira Gandhi Center for AtomicResearch (IGCAR), HBNI, Kalpakkam -603 102, India
Sujay Chakravarty
UGC-DAE Consortium for Scientific Research (CSR) Kalpakkam Node, Kokilamedu,Tamil Nadu -603 104, India

Abstract


Cr-Nb-Cr trilayer thin films were deposited using DC/RF sputtering with Cr layer thickness maintained at 7.5 nm and Nb thickness varying from 30 nm to 229 nm, in order to study the interplay of antiferromagnetism and superconductivity. Various viewpoints have been expressed in the literature with respect to analyzing the anomalous properties that have been identified in superconductor/magnetic thin films. The study of Cr-Nb-Cr thin films were taken up to identify the existence of similar anomalous superconducting properties on account of antiferromagnetic-superconductor interfaces. X-ray reflectivity measurements showed high quality of thin film structure with minimum surface and interface roughness. Transport measurements down to 2K were carried out in the presence of magnetic fields up to 2 T applied perpendicular to the trilayers to deduce Tc. The suppression of Tc due to Cr layer is larger than proximity effect of similar metal films. It could be explained by proximity effect using antiferromagnetic Cr layer. Upper critical field measurements show a distinct non monotonic dependence of upper critical magnetic field and the slope on Nb layer thickness. The analysis due to WHH theory to deduce upper critical fields for the trilayer thin films studied did not match with experimental values. Although studies performed on Cr-Nb-Cr trilayers did not show any anomaly in Tc, it clearly showed a depression of Tc much larger than proximity effect, non monotonic behavior in Bc2(0) and dBc2/dTc behavior with Nb layer thickness.