Magnetic properties of nanostructured Tb-Fe alloy thin films

Nanostructured ferrimagnetic Tb-Fe alloy thin films were prepared on pre-patterned substrates as underlying template, consisting of nanodot arrays with a dot diameter of 30 nm and a period of 60 nm. Two distinct magnetic configuration are possible, one where the magnetic material on the nanodot and in the trenches is decoupled from each other for film thicknesses below the nanodot height, and the other where full exchange coupling between magnetic material on the dots and in the trenches is effective for magnetic films thicker than the nanodot height. Regardless, of the magnetic configuration the reversal of the magnetic material on top of the nanodots is found to be nucleation dominated, while the magnetic material in the trenches reverses via domain wall propagation, as confirmed by in-field magnetic force microscopy. The distinct behavior in this system is attributed to the reduced exchange stiffness followed by relatively narrow domain walls (approx. 3-4 nm) present in these rare earth - transition metal alloys. A systematic study of magnetic properties on nanostructured Tb-Fe alloy films as a function of composition and film thickness will be presented.