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Previous studies on epitaxial Fe3O4 rings in the context of spin-transfer torque effect have revealed complicated and undesirable domain structures, attributed to the intrinsic fourfold magnetocrystalline anisotropy in the ferrite. In this Letter, we report a viable solution to this problem, utilizing a 6-nm-thick epitaxial Fe3O4 thin film on GaAs(100), where the fourfold magnetocrystalline anisotropy is negligible. We demonstrate that in the Fe3O4 planar wires patterned from our thin film, such a unique magnetic anisotropy system has been preserved, and relatively simple magnetic domain configurations compared to those previous reports can be obtained.

A button and stripline beam position monitor (BPM) were designed and developed to achieve sub-micron orbit stability in the High Energy Photon Source (HEPS). Analytical formulae and CST electromagnetic simulation software were used to calculate the radio frequency characteristics of the BPM. The BPM design procedure was developed according to the HEPS requirements. The characteristic impedances of the stripline were designed to be 50 Ω and confirmed by measurements. The position sensitivity, position resolution, capacitance, and wakefield impedance of the button BPM were calculated. The measurement results confirmed that the design satisfied the HEPS requirements.

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