Properties Of FeNiSm Thin Films

Soft magnetic materials are widely used in electromagnetic sensors. With the rapid developing of electromagnetic devices, the requirements for high frequency soft magnetic thin films are more demanding. In this paper, the FeNiSm thin films were prepared by radio frequency (RF) magnetron co-sputtering onto Si (111) substrates. The properties of FeNiSm films were studied by X-ray diffraction (XRD), surface profilometer, scanning electron microscopy, transmission electron microscopy, magnetic force microscopy (MFM), vibrating sample magnetometer (VSM), ferromagnetic resonance (FMR). The results are as follows:1. The magnetic properties of FeNiSm thin films with different thickness, different Ta interlayer thicknesses and different numbers of Ta interlayers were investigated. The single layer FeNiSm shows in-plane uniaxial anisotropy at a thickness below a critical value, but shows weak perpendicular anisotropy with a stripe domain structure at thicknesses above the critical value.2. Experiments indicate that one or more Ta interlayers inserted into thick FeNiSm films with weak perpendicular anisotropy were effective not only to cancel the perpendicular anisotropy, but also to recover the in-plane uniaxial anisotropy. The reason for recovery of the in-plane anisotropy of thick FeNiSm by introducing Ta interlayers is that blocking of the columnar growth of FeNi grains by the Ta interlayer.3. The angular dependence of the remanence ratios in a 200 nm FeNiSm film with one 6 nm Ta interlayer and a homogeneous 100 nm FeNiSm film are both very well described by a|cosθ| dependence, indicating that the in-plane uniaxial anisotropy was obtained. Here 0 is the angle between the easy axis and the magnetic field.4. The angular dependences of coercivity of a 200 nm FeNiSm film with one 6 nm Ta interlayer and a homogeneous 100 nm FeNiSm film is well described by the Kondorsky model when the applied field is near the easy axis and by the coherent rotation model when the applied field is close to the hard axis, indicating the magnetization reversal mechanism can be well describe by the domain wall unpinning and coherent rotation of magnetizaiton when the magnetic field applied along the easy axis and hard axis, respectively.5. Both a 200 nm FeNiSm film with one 6 nm Ta interlayer and a homogeneous 100 nm FeNiSm film have good high frequency properties. The calculated permeability spectra are consistent with those of experimental with damping constantsαof 0.22 and 0.25, respectively.