Magnetic switching properties of Fe-Ni-Pt thin films with graded magnetocrystalline anisotropy

Exchange-coupled composites and graded magnetocrystalline anisotropy Ku films allow a lower switching field while maintaining a given thermal stability relative to a conventional single Ku thin film. In this letter, [001] oriented single composition, multilayered single compositions, and a linearly graded composition of L1₀FexNi_0.48-xPt_0.52 thin films were sputter-deposited. The films were patterned into an array of ~70-80 nm diameter nanodots by electron beam lithography and Ar ion etching. A relative improvement in the switching field-to-thermal stability of ~41% was achieved for the continuous graded film as compared to the single composition Fe_0.23Ni_0.25Pt_0.52 film. However, the patterned diameter size was still too large to prevent lateral magnetic domain wall motion; consequently, the absolute switching field-to-thermal stability value was low.