The Magnetic Domain Evolution In Rare Earths And Transition Metals Multilayers And Their Patterns

The magnetic moments of rare earth(RE)and transition metal(TM)are antiferromagnetically coupled in RE and metal(TM)composite multilayer films and the anisotropy of the REs are very sensitive to temperature.Thus,it is easy to tune the magnetic anisotropy and magnetic compensation point by varying the thickness of the layers,the composition of the RE/TM and the temperature.Base on the RE/TM multilayer films,the topological magnetic structures of the patterned and nanocomposite multilayer films are easily investigated,such as the magnetic bubbles,skyrmions,vortex.Because of their unique reversal mechanisms and topological stability,they have a huge potential in information storage applications.Fe/Gd multilayers and[Tb/Co]n/Ru/Co nanocomposite multilayers were prepared by high vacuum magnetron sputtering,the corresponding patterns were prepared by combining different micro-nanomachining methods.Fe/Gd nanodots were prepared by combining porous anodized aluminum oxide(AAO)template and Ar ion etching,and[Tb/Co]n/Ru/Co micro disks were prepared by combining ultraviolet photolithography and Ar ion etching.The morphology,magnetic properties and magnetic domains were measured by SEM,AFM,SQUID,MFM,etc.The AAO template of more than 500 nm was successfully prepared by improved a conventional two-step anodization process,and the well-arranged Fe/Gd nanodots were prepared by combining magnetic sputtering,AAO template method and Ar ion etching.Magnetic measurement results show that,as the thickness of the multilayer films increases,the increase of PMA leads to the formation of the perpendicular magnetic domains.The MFM technology was used to observe the magnetic domain of multilayers and nanodots,different from the stripe domain in continuous film.The magnetic bubbles are favored in nanodots at room temperature and in zero field due to the competition of the magnetostatic energy,anisotropy energy and exchange energy.When the temperature decreases to 20 K,the width of the stripe domains increases in the continuous film and the domain reversal mechanisim in nanodots,which is similar to a single-domain reversal behavior due to the increase of the perpendicular anisotropy.The[Tb/Co]n/Ru/Co nanocomposite disks were prepared by combining ultraviolet photolithography and Ar ion etching.The spontaneous formation of topological double-vortices were studied by tuning the thickness of spacer Ru layer and soft Co layer and the temperature.The MFM technology was used to observe the evolution of the double-vortex and the vortex,including the motions of the two vortices with two opposite chirality and the change from double-vortex to the vortex.At low temperatures,the motions of double-vortex disappear due to the increase of the soft and hard magnetic coupling and the anisotropy of hard-magnetic layer.Our results demonstrate the importance of the interlayer exchange interactions in the formation of the topological configuration in a nanocomposite magnetic structures.