Structure, microstructure and magnetic properties of Ni 75 Fe 25 films elaborated by evaporation from nanostructured powder

Abstract

We report on the structural, microstructural and magnetic properties of Ni 75 Fe 25 permalloy (Py) thin films. Py thin films with different thicknesses were deposited by vacuum evaporation from nanocrystalline powder onto Si (11) substrate. The thickness varies from 16 nm to 250 nm. From grazing X-ray diffraction patterns (GIXRD), we have shown the presence of a strong (200) texture for the lowest thickness (16 nm). For the 52 nm and 84 nm thick samples, a strong (111) preferred orientation is developed. However, for higher thicknesses, a polycrystalline structure is present. From the Scanning Electron Microscopy observations (SEM), we have shown that the surface seems to be very dense with many fine grains. The analysis of EDX spectra revealed that the sample composition is close to the starting Ni 75 Fe 25 powder. A more accurate investigation of the morphology was performed with the atomic force microscopy (AFM). We have shown the existence of nanosized grains with a uniform distribution. The mean diameter of the grains increases from 27 nm to 40 nm when the thickness increases. From magnetic measurements, we have shown the existence of a uniaxial magnetic anisotropy with an easy axis parallel to the film plane. The coercive field, H C was found to decrease with increasing thickness.