Spontaneous formation of spiral-like patterns with distinct periodic physical properties by confined electrodeposition of Co-In disks

Abstract

Spatio-temporal patterns are ubiquitous in different areas of materials science and biological systems. However, typically the motifs in these types of systems present a random distribution with many possible different structures. Herein, we demonstrate that controlled spatio-temporal patterns, with reproducible spiral-like shapes, can be obtained by electrodeposition of Co-In alloys inside a confined circular geometry (i.e., in disks that are commensurate with the typical size of the spatio-temporal features). These patterns are mainly of compositional nature, i.e., with virtually no topographic features. Interestingly, the local changes in composition lead to a periodic modulation of the physical (electric, magnetic and mechanical) properties. Namely, the Co-rich areas show higher saturation magnetization and electrical conductivity and are mechanically harder than the In-rich ones. Thus, this work reveals that confined electrodeposition of this binary system constitutes an effective procedure to attain template-free magnetic, electric and mechanical surface patterning with specific and reproducible shapes.

Figure 1

FE-SEM images of (a) an array of Co–In microdisks (taken with In-Lens detector), (b) detail of one microdisk taken with SE detector and (c) corresponding image obtained using the In-Lens detector.

Figure 2

EDX mapping of a Co–In microdisk.

Figure 3

(a) AFM topographical and (b) current map image taken with the C-AFM under a constant applied load of 50 nN on 35 × 31 μm² scanned area of a Co-In microdisk.

Figure 4

(a) In-Lens SEM image of a Co-In microdisk showing the positions onto which the MOKE laser was focused. (b) Polar (out-of-plane) room-temperature MOKE magnetic hysteresis loops for different positions across the diameter of the disk. (c) Dependence of the maximum Kerr amplitude as a function of position.

Figure 5

(a) AFM topography and (b) In-Lens SEM image of the Co-In microdisk. (c) MFM image at remanence after saturation at 1 T in plane. The image was taken in double pass mode, by scanning at a lift height of 30 nm with the same amplitude of oscillation as that used as setpoint for topography. Mapping of (d) work function acquired by KPFM using a tip voltage of 1 V, (e) normalized Young’s modulus and, (f) penetration depth (in nm) measured in AM-FM viscoelastic mapping mode.

Figure 6

(a) XAS-PEEM (elemental map) and (b,c) XMCD-PEEM images at the Co L-edge. (b,c) are measured in remanence after applying a saturating field (650 Oe) in the (b) positive (+M_R) and (c) negative (−M_R) in-plane direction.