Magnetic properties of rare earth transition metal compositionally-modulated films

The experimental investigation of magnetic and structural properties for RE/TM (RE = Dy, Tb, Gd, Er, Nd, and TM = Fe, Co, Ni) compositionally-modulated films (CMF) is reported. A detailed theoretical model for the distribution of magnetization and anisotropy along the film normal and the origins of the perpendicular anisotropy is discussed. The magnetization, anisotropy, coercivity were found to change regularly as a function of the RE and TM layer thicknesses. In particular, systematic studies have been performed for Dy/Co and Dy/Fe CMF at layer intervals of about one atomic diameter, for layer thicknesses up to about 20 A. Ferromagnetic coupling for light RE/TM and antiferromagnetic coupling for heavy RE/TM were observed. The temperature dependences of the magnetization, anisotropy and coercivity for selected RE/TM CMF have been studied. RE/TM CMF (RE = Dy, Tb, Nd, Gd, and TM = Fe, Co) with layer thicknesses less than about 10 A exhibit perpendicular magnetic anisotropy (PMA) and the range of the layer thicknesses required for perpendicular anisotropy is determined. Dy/Co, Dy/Fe and Tb/Fe CMF may be promising candidates for perpendicular magnetic and magneto- optic recording because of their strong and controllable perpendicular anisotropy. A model was developed to understand the micro-magnetic properties of RE/TM CMF. The magnetization was analyzed using a modified meanfield model, and the anisotropy was treated using a single-ion model for REs possessing orbital angular momenta. The calculated results based on these models agree well with the experimental data