Microstructural and magnetic studies of granular GdW films

We have studied the microstructural and magnetic properties of sputtered nanocrystalline granular Gd-W thin films as a function of annealing temperature. Granular Gd-W films were formed by annealing the as-deposited amorphous films in the temperature range 700–950 °C for 15 min. The TEM studies on the annealed samples indicate that the Gd and W phases crystallize as separate phases around 825 °C. The grain sizes of these granular phases were estimated to be about 10–30 nm. Magnetic measurements of samples annealed at 875 °C indicate the coexistence of superparamagnetic Gd with a blocking temperature near 50 K and ferromagnetic Gd with a Curie temperature near 293 K. Higher temperature annealings led to bulk-like ferromagnetic Gd behavior.