Effect of thermal annealing on Fe₄₀Ni₃₈B₁₈Mo₄thin films: modified Herzer model for magnetic evolution

Abstract

Magnetic properties of nano-crystalline soft magnetic alloys have usually been correlated to structural evolution with heat treatment. However, literature reports pertaining to the study of nano-crystalline thin films are less abundant. Thin films of Fe 40 Ni 38 B 18 Mo 4 were deposited on glass substrates under a high vacuum of ≈ 10 −6 Torr by employing resistive heating. They were annealed at various temperatures ranging from 373 to 773 K based on differential scanning calorimetric studies carried out on the ribbons. The magnetic characteristics were investigated using vibrating sample magnetometry. Morphological characterizations were carried out using atomic force microscopy (AFM), and magnetic force microscopy (MFM) imaging is used to study the domain characteristics. The variation of magnetic properties with thermal annealing is also investigated. From AFM and MFM images it can be inferred that the crystallization temperature of the as-prepared films are lower than their bulk counterparts. Also there is a progressive evolution of coercivity up to 573 K, which is an indication of the lowering of nano-crystallization temperature in thin films. The variation of coercivity with the structural evolution of the thin films with annealing is discussed and a plausible explanation is provided using the modified random anisotropy model.

Structural, topographical and magnetic evolution of RF-sputtered Fe-Ni alloy based thin films with thermal annealing

“…As a result of higher oxidation of the film, the saturation magnetization is further reduced. Earlier studies by Hysen et al [19] and Senoy et al [20] on the annealing effects of FeNiMoB thin films by thermal evaporation showed that Mo and B were not present in the film. The Fe Ni phase precipitated on annealing, resulting in a nanocrystalline structure exhibiting high saturation magnetization.…”

“…Compared to the bulk FeNiMoB ribbons, the films show a low value of saturation magnetization. Hysen et al [19] have reported a saturation magnetization of 70 emu g −1 for annealed films of Fe-Ni. In this investigation we obtained a very low value of saturation magnetization for the annealed film.…”

“…Jyothi et al did not carry out composition analysis; they found that the deposited films were crystalline. Senoy et al and Hysen et al reported the fabrication of thin films from composite targets using vacuum evaporation [19,20]. They also studied annealing and swift heavy ion irradiation effects on these films and reported the formation of Fe-Ni nanocrystals with annealing [21,22].…”

Metglas thin film based magnetostrictive transducers for use in long period fibre grating sensors

“…Vapour deposition offers a simple alternative to sputter deposition in obtaining thin films of supersaturated solid solutions and other metastable states. Some attempts to prepare Metglas 2826 MB thin films by thermal evaporation have been reported in the literature [10][11][12][13][14][15]. Thin films of Fe 40 Ni 38 Mo 4 B 18 were prepared by the flash evaporation technique [10].…”

“…Magnetic studies were not carried out on these samples and the main focus of the paper was on the structural evolution of these films with thermal annealing. An alloy film deposited from a target of composition Fe 40 Ni 38 Mo 4 B 18 was studied previously by our group [11][12][13][14][15]. When Metglas thin films are grown it is necessary that their composition is determined as accurately as possible and technique like XPS is very useful in such studies.…”