Electrodeposited CoNiFeP Soft-Magnetic Films for High-Frequency Applications

We have studied the influence of P and of plating current density on static/dynamic magnetic and electrical properties of CoNiFe high moment alloy. We found that morphology, electrical and magnetic properties of films with P content up to 10 at. % are quite different from those of pure CoNiFe. CoNiFeP morphology consists of a structure made of isolated islands with sizes varying between 10 and 50 mu m. We indirectly obtained resistivity in this structure by using high-frequency magnetic measurements. Film composition is weakly dependent on plating current density for values larger than 10 mA cm^-2. Coercivities increase up to 6400 A m^-1 and magnetization saturation is reduced to 1.0 T in CoNiFeP films. The most remarkable effect of P addition to CoNiFe is the increase of resistivity over two order of magnitude with values of 5.2x10^-5 Omegam compared to 2.4x10^-7 Omegam of pure CoNiFe. We also found that the ferromagnetic resonance of CoNiFeP alloy is 3 GHz for sample with 10 at. % P and a performance factor (BF) of ~ 4x10⁵ T s^-1, which is a better performance than bulk ferrite.