Superconducting Transport Properties of NiFe Artificial Spin Ice and Nb Hybrid Structure
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ORIGINAL PAPER
Superconducting Transport Properties of NiFe Artificial Spin Ice and Nb Hybrid Structure Apoorva Verma 1,2 & Mandeep Kaur 1 & T. D. Senguttuvan 1,2 & Anurag Gupta 1,2 Received: 22 August 2020 / Accepted: 28 September 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract We report the influence of magnetic NiFe artificial spin ice (ASI) on the transport properties of superconducting Nb thin film. Resistivity (ρ) as a function of temperature (T ~ 1.8 to 300 K) and magnetic field (B ~ 0 to 40 kOe in parallel and perpendicular orientations with respect to the film plane) has been examined for two samples, a plain Nb thin film and a hybrid thin film of NiFe-ASI and Nb (Nb-NiFe). The impact of the magnetic NiFe-ASI on superconducting Nb is clearly visible in the transport properties, where, in comparison with plain Nb, for the Nb-NiFe hybrid thin film: (1) the normal state resistivity increases by a factor ~ 1.5; (2) the superconducting transition temperature (Tc) at B = 0 reduces from 7.31 to 6.51 K; (3) the surface sheath superconductivity vanishes as reflected by the parallel upper critical field, Bc2(T); and (4) the perpendicular Bc2(T) is suppressed Nb−NiFe in the entire T range. Interestingly, with the applied field, T Nb |B increases in perpendicular and decreases in parallel c −T c field orientation. The magnetoresistance measurements near Tc for our Nb-NiFe hybrid thin film show shallow minima revealing matching pinning effects with respect to the ASI square lattice. The results are understood in terms of the thin film nature of our samples, geometrically frustrated magnetism of ASI and the proximity between the magnetic NiFe-ASI and superconducting Nb at the interface. Keywords S/F hybrid . Artificial spin ice . Proximity effect . Transport properties
1 Introduction The interplay of the competing magnetic and superconducting order parameters in hybrid nanostructures of superconductors (S) and ferromagnets (F) has led to novel physics and various applications over the years [1–6]. Various S/F hybrid nanostructures have been looked into and numerous phenomena have emerged as a consequence of the interacting S and F layers, such as the reduction of Tc [7–9], oscillating Tc due to 0 and π-phase coupling [10–12] and domain wall superconductivity [13–15]. When the F layer consists of periodic magnetic nanostructures such as dots, rings etc., it can control and manipulate vortex dynamics or modify the pinning forces, thus enhancing the critical current performance of the underlying superconductor [16–21]. Recently, a new and interesting * Anurag Gupta [email protected] 1
CSIR-National Physical Laboratory, New Delhi, India
2
Academy of Scientific & Innovative Research, CSIR-National Physical Laboratory, New Delhi, India
periodic magnetic system called artificial spin ice (ASI) has become widely investigated whose magnetism is driven by frustration and non-equilibrium magnetic dynamics, unlike simpler nanostructures such as dots and rings [22–29]. The ASI system consi
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