Kaur, M. and Gupta, Anurag and Varandani, D. and Verm, Apoorva and Senguttuvan, T. D. and Mehta, B. R. and Budhani, R. C. (2017) Magnetic reversal dynamics of NiFe-based artificial spin ice: Effect of Nb layer in normal and superconducting state. Journal of Applied Physics , 122 (193903). pp. 1-6. ISSN 0021-8979

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Abstract

Square arrays of artificial spin ice (ASI) constituting weakly interacting NiFe nano-islands, with length similar to 312 nm, width similar to 125 nm, thickness similar to 20 nm, and lattice constant similar to 570 nm, were fabricated on Nb thin film and on thermally grown 300 nm SiO2 on silicon. Detailed investigations of magnetic force microscopy (MFM) at room temperature, and magnetization M(H) loops and relaxation of remanent magnetization (M-r) at various temperatures were carried out in two in-plane field geometries, namely, parallel ("P"-parallel to the square lattice) and diagonal ("D"-45 degrees to the square lattice). The magnetic response of the ASI samples shows striking difference for insulating (SiO2), metallic (Nb, T > 6.6 K) and superconducting (Nb, T < 6.6 K) bases, and the field geometry. For instance, with the Nb base in the normal metallic state (T > 6.6 K), (1) in "P" geometry the M(H) loops are found to be more "S" shaped in comparison with that for SiO2 base; (2) the ratio of magnetic vertex population of Type II to Type III vertices extracted from MFM studies in "P"("D") geometry is similar to 1:1.1(1.2:1) that changed for the SiO2 base to similar to 2.1:1 (4:1). However, the NiFe-ASI on both metallic Nb and SiO2 bases exhibit a highly athermal decay of magnetization, and the % change in Mr in about two hours at T = 10K (300 K) lies in a range of similar to 1.07-1.80 (0.25-0.62). With Nb base in superconducting state (T < 6.6 K), the M(H) loops not only look radically different from those with SiO2 and metallic Nb as bases but also show significant difference in "P" and "D" geometries. These results are discussed in terms of inter-island magnetostatic energy as influenced by field geometry, presence of metallic Nb base and competing vortex pinning energy of superconducting Nb base.

Item Type:	Article
Additional Information:	Copyright for this article belongs to M/s American Institute of Physics.
Subjects:	Applied Physics/Condensed Matter
Divisions:	UNSPECIFIED
Depositing User:	Users 27 not found.
Date Deposited:	12 Nov 2018 07:14
Last Modified:	12 Nov 2018 07:14
URI:	http://npl.csircentral.net/id/eprint/2782

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