Effect of patterning on SmCo micromagnets suitable for integration in microsystems

The integration of micromagnets in microsystems is still at its infancy. There is no well-established technology for patterning permanent magnets with in-plane resolution and thickness on the order of 1 µm, which is highly desirable for obtaining sizable stray fields in integrated devices. Here we report on the magnetic and structural properties of the W(100)/SmCo(500)/W(100) heterostructure (thickness in nm) after patterning by ion beam etching. Continuous trilayers W/SmCo/W are deposited by sputtering on a Si/SiO2 substrate and then annealed at 650 °C to achieve a remanence magnetization μ0Mr = 0.45 T. Rectangular micromagnets (150 × 20 × 0.5 μm3) are then patterned by ion beam etching. The patterning does not significantly affect the magnetic properties of the SmCo film, apart from the appearance of a vertical shift in the hysteresis loops measured in the ± 2 T range, which is ascribed to the hardening of magnetic phases upon ion bombardment. As a side effect of etching, tapered edges of the magnets are obtained. However, the stray field generated above 1 µm height from the magnets is not significantly perturbed by a tapering with an angle up to 45 degrees. This work demonstrates the suitability of our fabrication process for the integration of SmCo permanent micro-magnets in micromechanical system (MEMS).