Characterization of Fe Micromagnets for Semiconductor Spintronics by In-Field Magnetic Force Microscopy

Recent developments in quantum electronics, particularly spin-qubit systems and semiconductor spintronics, provide new applications for micromagnets. The stray field of properly placed micromagnets can be employed to manipulate spin-qubits using rf-signals. Micromagnets are used as the injector and detector contacts in semiconductor spintronics. For both applications, single-domain magnets with precisely known magnetic properties, with and without external field, are required. We report on Fe micromagnets with different aspect ratio, fabricated using standard semiconductor processing technology. We describe a simple setup using a custom-built electromagnet and conventional atomic force microscope to characterize the micromagnets in an external magnetic field using magnetic force microscopy (MFM). We use this setup to characterize the fabricated micromagnets' domain structure and switching behaviour. We show that MFM, together with the custom-built electromagnet is a simple, yet versatile method to characterize micromagnets for applications in quantum electronics. We furthermore show that the fabricated micromagnets all exhibit the desired single-domain state. The micromagnets differ in their coercive field, depending on the aspect ratio. This makes these micromagnets suitable for spin-injection and spin-detection.