Shape-induced ultrahigh magnetic anisotropy and ferromagnetic resonance frequency of micropatterned thin Permalloy films

Magnetic anisotropy H-k>200 Oe was observed from bar-shaped Permalloy strips. The film was deposited on sputtered Cr seed layer by electroplating under similar to 800 Oe external magnetic field. Tiny degradation of H-k was observed after 30 min postannealing at 400 degrees C in the absence of external magnetic field. The Permalloy strip with in-plane aspect ratio of 40:1 showed the ferromagnetic resonance at similar to 5.3 GHz. The ferromagnetic resonance frequency and magnetic anisotropy decreased to similar to 1 GHz and similar to 50 Oe, respectively, as the in-plane aspect ratio reduced from 40:1 to 10:1. In comparison, Permalloy strips plated on combined Ti/TiN seed layers did not show clear anisotropy features. (C) 2006 American Institute of Physics.