Tailoring Magnetic Domains and Magnetization Switching in CoFe Nanolayer Patterns with Their Thickness and Aspect Ratio on GaAs (001) Substrate

Abstract

The thickness and aspect ratio dependence of magnetic domain formation in CoFe nanolayer patterns on GaAs (001) substrates are investigated by means of a direct approach using magnetic force microscopy at room temperature. Magnetic force microscope observations under as‐deposition condition show that magnetic domain formation in the patterns depends strongly on the aspect ratio and thickness of the patterns and the crystallographic orientations of the substrates. A single magnetic domain is more easily formed in the patterns with a higher aspect ratio, with a thinner nanolayer thickness, and along the ⟨110⟩ direction of the substrates. The magnetic fields are next applied in the direction parallel to the ⟨1–10⟩ and ⟨110⟩ orientations of the substrates to characterize a magnetization switching behavior in the patterns. The aspect ratio and thickness of the patterns and the crystallographic orientations of the substrates strongly affect the magnetic fields needed for magnetization switching in the patterns. A higher magnetic field is required for a higher aspect ratio and a thinner nanolayer thickness of the patterns. All the direct observations confirm that the magnetic domain structures and magnetization switching are tuned by controlling aspect ratio and thickness of the patterns and the crystallographic orientations of the substrates.

Magnetic domain control and its dependence on aspect ratio and thickness in Ni nanolayer patterns for nanowire spintronic devices

“…3(a) and 3(b), the appearance of dark and light "tessellated" magnetic domain patterns implies that the magnetic domains are neatly aligned, and that the magnetization of adjacent domains is in the opposite direction. Similar patterns are reported in the article by K. Teramoto et al, 47) in which well-defined "double" magnetic domain patterns, as illustrated in Fig. 2(j).…”

“…We have been demonstrating that the MFM is a powerful direct observation tool to systematically analyze an actual magnetic domain formation controlled in the patterned structures of ferromagnetic nanolayer electrodes. 47) The objective of this article, therefore, is to analyze a magnetic domain structure of Ni nanolayer electrodes by our direct approach using MFM, as anomalous magnetotransport properties and the large MR effect have been observed in lateral Si NW devices with ferromagnetic Ni nanolayer electrodes. 32) By designing and investigating Ni nanolayer electrode patterns with a different aspect ratio and thickness, the ways to control a magnetic domain and obtain a single magnetic domain are demonstrated and discussed for the NW spintronic devices.…”

Incremental Analysis of Magnetic Domains in Multiple Types of Ferromagnetic CoFe Nanolayer Patterns

“…We prepared the 4 Â 4 array of CoFe NPs with the same 16 aspect ratios as those in our previous article, Ref. [20], for comparison. Each of designed size, that is, length and width, of the CoFe NPs is described in black in Figure 1b, which is the same as that in Figure 1a.…”

“…Here, the switching behavior of magnetization in the patterns with a thickness of 10 and 20 nm was characterized additionally from the MFM observation results in our previous report, Ref. [20], for comparison. The sampling number of the characterizations for each of the four CoFe NPs in Figure 4 was three to five per one of the four observed patterns as we prepared several same samples including the four observed patterns of Is(2, 0.5), Is(2, 0.75), Is(0.75, 2), and Is(0.5, 2).…”

“…To achieve our long-term purpose, it is surely essential to investigate and understand the magnetic domain formation in the miniaturized ferromagnetic electrode patterns with a high aspect ratio as a large H c , or coercive force, and a single magnetic domain are expected in such an elongated structure of the patterns. We have been demonstrating in our previous study [20,21] that magnetic force microscope (MFM) is a powerful tool to…”