Role of diffused Co atoms in improving effective exchange coupling in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Sm</mml:mi><mml:mtext>−</mml:mtext><mml:mi>Co</mml:mi><mml:mo>∕</mml:mo><mml:mi>Fe</mml:mi></mml:mrow></mml:math>spring magnets

In $\mathrm{Sm}\text{\ensuremath{-}}\mathrm{Co}∕\mathrm{Fe}$ exchange-spring magnet films, the magnetization reversal processes of constituent elements and layers were studied with an emphasis on the role of diffused Co atoms. Enhanced coupling effectiveness was observed in a film with a graded interface where significant Co diffusion into the Fe layer was observed by means of electron microscopy. Comprehensive insight into the magnetization reversal processes was obtained by combining micromagnetic simulation with element- and depth-resolved x-ray resonant magnetic scattering. The approach unambiguously identifies distinctive composition profiles across the graded interface and provides the magnetization behavior of the diffused Co.