Growth and Shape-Ordering of Iron Nanostructures on Au Single Crystalline Electrodes in an Ionic Liquid: A Paradigm of Magnetostatic Coupling

Abstract

Fe electrodeposition on Au(111) and Au(100) in BMIBF(4) ionic liquid is found to form hitherto unreported shape-ordered nanoscale morphologies of pseudorods and pseudosquare rings, respectively, both composed of grains of 4-7 nm. The manner of growth of the square rings is a ring-on-ring structure with enlarging side length and slightly protruding four corners. The generality of the growth mechanism is verified by the formation of almost exactly the same shape-ordered Fe nanostructures on Pt, i.e., pseudorod structure on Pt(111) and pseudosquare rings Pt(100). These structures are explained within the framework of magnetostatic interactions of spontaneously magnetized grains under crystallographic constraint of the substrate surface, which result in an antiparallel arrangement in magnetization of the grains at pseudorods and magnetic flux closure at the pseudosquare rings. The closed magnetic flux further leads to magnetic field-enhanced growth at the four corners and the outer peripheries of the pseudosquare rings. The observed shape-ordering of the Fe thin film serves as a paradigm of magnetostatic coupling, in which the roles of ionic liquid as surfactant and magnetic media may not be underestimated. The present work adds a new dimension to electrodeposition in ionic liquid, by which new magnetic film structures may be expected.

The Electrode/Ionic Liquid Interface: Electric Double Layer and Metal Electrodeposition

“…Fe deposition on Au and Pt single-crystalline electrodes in [BMI] [BF 4 ] has been systematically studied in the authors' group. [159] Using FeCl 3 as the precursor, in situ STM results have shown that Fe is deposited with the formation of shape-ordered structures, namely pseudo-rods on Au(111) and pseudosquare rings on Au(100). These interesting structures are explained as results of magnetostatic interactions under crystallographic constraints.…”

Electrodeposition of CuZn from Chlorozincate Ionic Liquid: From Hollow Tubes to Segmented Nanowires

“…Regarding the electrodeposition of micro-/nanostructures from ILs, template-based methods have been adopted for the deposition of nanoporous Cu and Si using polystyrene spheres, Al, Ag, and Si nanorods and/or tubes using polycarbonate membranes, and CuZnSn nanorods using anodized aluminum oxide membrane. Template-free methods have also been used for the direct deposition of monodispersed metal nanocrystals, , (polyhedral) iron pseudorods and rings, and Te tubes . We have previously reported the direct deposition of hollow CuSn tubes from 1-ethyl-3-methylimidazolium dicyanamide (EMI-DCA) IL, and NiZn, FeCoZn, AuZn,and Co nanowire arrays from the corresponding metal chloride-EMIC ILs without the need for a template.…”

Stretching single atom contacts at multiple subatomic step-length

“…The morphology of Fe clusters changes to show unique pseudorod like and pseudo-square like structures on Au(111) and Au(100), respectively, which has been found to be characteristic of Fe electrodeposition on the respective surfaces. 49 Although one-to-one identification of the original cluster is not possible because of the overlap between the growing anisotropic structures and interference of growth from the cluster-free area, the protrusions of the deposit in the cluster region indicate enhanced growth at the clusters, which actually serve as growth centers. Obviously, the anisotropic growth behavior only could be preserved and observed in this region when the clusters are epitaxial with the surface structure.…”