Abstract
Transition metal alloys are essential for magnetic recording, memory, and new materials-by-design applications. Saturation magnetization in these alloys have previously been measured by conventional techniques, for a limited number of samples with discrete compositions, a laborious and time-consuming effort. Here, we propose a method to construct complete saturation magnetization diagrams for Co–Fe–Ni alloys using scanning Hall probe microscopy (SHPM). A composition gradient was created by the diffusion multiple technique, generating a full combinatorial materials library with an identical thermal history. The composition and crystallographic phases of the alloys were identified by integrated energy dispersive X-ray spectroscopy and electron backscatter diffraction. “Pixel-by-pixel” perpendicular components of the magnetic field were converted into maps of saturation magnetization using the inversion matrix technique. The saturation magnetization dependence for the binary alloys was consistent with the Slater-Pauling behavior. By using a significantly denser data point distribution than previously available, the maximum of the Slater-Pauling curve for the Co–Fe alloys was identified at ~ 32 at% of Co. By mapping the entire ternary diagram of Co–Fe–Ni alloys recorded in a single experiment, we have demonstrated that SHPM—in concert with the combinatorial approach—is a powerful high-throughput characterization tool, providing an effective metrology platform to advance the search for new magnetic materials.
Highlights
Materials property mapping as a function of composition and structure was accomplished through laborious and time-consuming synthesis and analysis of samples with discrete compositions prepared one at a time
As the first step of characterizing the diffusion of multiple interfaces, we performed a series of line scans across the three binary regions (Co–Fe, Co–Ni, and Ni–Fe) using scanning electron microscopy (SEM)
In this article, Scanning Hall probe microscopy was applied to investigate the composition-structure-magnetic properties of diffusion binary and ternary Co–Fe–Ni alloys fabricated by the diffusion multiple technique
Summary
Materials property mapping as a function of composition and structure was accomplished through laborious and time-consuming synthesis and analysis of samples with discrete compositions prepared one at a time. We used a scanning Hall probe microscope (SHPM) in a lift-off mode under ambient conditions to investigate and map the Co–Fe–Ni saturation magnetization by detecting magnetic field distributions near the surface of the sample with variable composition, with resolution limited only by the sample and the Hall Probe geometry (see Fig. 1). Several techniques, such as Bitter decoration[19], the Faraday rotation effect[20], Lorenz microscopy and electron h olography[21], magnetic force microscopy (MFM)[22] and Hall probe sensing[23], have been employed to detect surface magnetic fields While each of these techniques has distinctive advantages, SHPM combines many desirable features: it is noninvasive, has an excellent, potentially submicron spatial resolution and allows quantitative measurements of large magnetic fields with high sensitivity (no saturation). The source of the perpendicular (z-component) of the magnetic field measured by the SHPM can be understood by considering contributions from regions of different compositions within a simple dipole approximation
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