Geometric shape dependence of coercivity for patterned magnetic thin films

The micro-strips with patterned magnetic domains using electron beam lithography have been made to study the geometric shape dependence of coercivity. The size of the micro-strip is 10 μm×30 μm with 0.5 μm periods hole arrays pattern. Arrays with different types of geometry, such as square-, circle-, and ellipse-shapes have been made. Amorphous rear-earth transition-metal (RE-TM) thin films with magnetic perpendicular anisotropy were deposited on the microstrips. The extraordinary Hall effect has been employed to measure the hysteresis loop and the coercivity of the sample. We have found that for the same deposited material, the magnitude of coercivity for various shapes are dissimilar. For example, the coercivity of the ellipse-shaped hole arrays is much larger than the coercivity of the square-shaped hole arrays. In addition, we observed that the coercivity of the patterned sites was larger than the sites without patterns for RE-dominated compounds and the coercivity of the patterned sites was smaller than the sites without patterns for TM-dominated compounds. The magnetic moments canting between RE and TM subnetworks will be used to explain the observed phenomena.