Correlation of Interface Structure with Magnetic Exchange in a Hard/Soft Magnetic Model Nanostructure

So-called ``exchange-spring magnets'' are important for synthesizing rare-earth-free permanent magnets with a high energy product, but the latter is limited by the critical thickness of the soft magnetic phase, above which exchange coupling deteriorates. Thus understanding the physics of exchange coupling is necessary to overcome that technical difficulty. This study uses experiment and theory to build up a model system that allows systematic analysis of exchange interactions in a MnGa/FeCo bilayer exchange system. The significant roles of epitaxial growth and hard/soft interfacial properties offer engineering solutions for multilayered exchange-spring magnets in $e.g.$ electric motors.