( FeCo/Co–M ) n soft magnetic multilayers with uniaxial anisotropy and very high saturation magnetization

Abstract

Nanocrystalline (FeCo/CoNbZr)n and (FeCo/CoZr)n uniaxial-anisotropy soft magnetic multilayers with saturation flux density up to 22.5 kG were prepared by rf sputtering. Magnetic and microstructural properties of these films were studied before and after magnetic annealing. Cross-sectional transmission electron microscopy study showed that the soft magnetic Co–M (M=Zr, Nb, etc.) amorphous layers act as grain refiners as well as soft magnetic grain-boundary materials for the FeCo layers. The resultant multilayer films exhibit excellent uniaxial-anisotropy soft magnetic properties with small coercivity, high anisotropy field Hk, and excellent thermal stability after magnetic field annealing, which are very attractive for applications in thin-film heads for ultrahigh-density magnetic recording. The origin of the soft magnetism was discussed in the light of the random anisotropy model. The improvement of soft magnetic properties of the laminated films is closely associated with the reduction in grain size of the FeCo layers due to lamination. Qualitative agreement between the experimental data and theoretical calculations can be established. Magnetic field annealing was very effective in improving the soft magnetic properties of the films. However, further study is required in order to understand the mechanism. The saturation magnetization of the film follows a simple summation function of the saturation magnetization of the two sublayer materials, with a maximum achievable value of 22.5 kG within the uniaxial-anisotropy regime.

Heavy Ion Irradiated Ferromagnetic Films: The Cases of Cobalt and Iron

“…Among the known soft magnetic materials, Fe 1 j x Co x alloys have the highest saturation magnetization (õ2.45 T), but due to their large coercivity they are not suitable for magnetic write heads [34]. Efforts to develop materials with low coercivity have been made, based on FeCoN [34] and laminated FeCoV films [35]. It is well known that for Co/Fe bilayers, the microstructure and magnetic properties of the underlayer play an important role during the cooperatively coupled domain-wall movement [36].…”

Effect of Co underlayer on soft magnetic properties and microstructure of FeCo thin films

“…Hence, an effective method to give rise to soft magnetic properties in Fe 65 Co 35 thin films must be investigated. Much effort such as optimization of deposition process [2], lamination with an amorphous layer [3], addition of a third element [4,5], and implementing a suitable buffer layer [6][7][8], has been taken. A lot of researchers pay attention to the effect of buffer layer and find that it can induce an exchange coupling [4], reduce the grain size [9,10], control the lattice strain and films stress [11,12], or change the film texture [13] in FeCo thin films.…”

Depth-resolved investigation of the lateral magnetic correlations in a gradient nanocrystalline multilayer

“…35 The same FeCoV ferromagnet is also implemented in multilayer structures for applications in spintronics. 37,38,[65][66][67][68] In Sec. V A, a detailed investigation of the remagnetization process by polarized neutron reflectivity with polarization analysis is presented, confirming the previous investigations.…”

“…36 All this, together with the high saturation magnetization of the ferromagnetic layers makes FeCoV an excellent candidate for high-frequency thin film read-head material. 37,38 In this supermirror, the lateral grain size increases with the layer thickness, 39 leading to an increase of the coercive field from the thinnest to the thickest layers. 34 The issue here is to figure out whether the evolution of the lateral grain size reflects itself in an evolution of the layer magnetization reversal mechanism and/or of the lateral magnetic correlations.…”