Based ‘Donut’ Micromagnets*

The development of next-generation computing devices based on spintronics and magnonics requires an understanding of how spin textures can be tailored in patterned magnetic materials. Lithographically patterned micro/nanostructures can provide insights into the formation of magnetic domains consisting of vortex states that are potential building blocks of magnetic memory. Complex oxide such as epitaxially grown La_0.7Sr_0.3MnO₃ (LSMO) thin films exhibit strong correlations among spin, orbital, charge and lattice parameters. As a soft ferromagnet, LSMO is a promising material for analyzing complex spin textures and controlling domain configurations by varying the micromagnet geometry. Using x-ray photoemission electron microscopy we imaged thermally demagnetized LSMO donuts i.e., circular micromagnets with variable hole diameters. The combination of quantitative image analysis and micromagnetic simulations, allowed us to explain the formation of spin textures consisting of either a single vortex or a pair of concentric vortices with opposite chiralities in the donut structures. These results further our understanding of magnetic spin texture formation and vortex dynamics for the development of spin-based devices.