Nanocrystallization and amorphization induced by reactive nitrogen sputtering in iron and permalloy

Abstract

Thin films of iron and permalloy (Ni80Fe20) were prepared using an Ar+N2 mixture with magnetron sputtering technique at ambient temperature. The nitrogen partial pressure, during sputtering process was varied in the range of 0 ≤ RN2 ≤ 100%, keeping the total gas flow at constant. At lower nitrogen pressures (RN2 ≤ 33%) both Fe and NiFe, first form a nanocrystalline structure and an increase in RN2, results in formation of an amorphous structure. At intermediate nitrogen partial pressures, nitrides of Fe and NiFe were obtained while at even higher nitrogen partial pressures, nitrides themselves became nanocrystalline or amorphous. The surface, structural and magnetic properties of the deposited films were studied using x-ray reflection and diffraction, transmission electron microscopy, polarized neutron reflectivity and using a DC extraction magnetometer. The growth behavior for amorphous film was found different as compared with poly or nanocrystalline films. The soft-magnetic properties of FeN were improved on nanocrystallization while those of NiFeN were degraded. A mechanism inducing nanocrystallization and amorphization in Fe and NiFe due to reactive nitrogen sputtering is discussed in the present article.

Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

“…32,33 For the sample prepared at R N 2 = 5%, the structure remains similar to 0% sample, but peak widths become broader due to interstitial incorporation of N atoms. 34 As R N 2 increases to 10%, the structure changes and reflection corresponding to Co 4 N(200) can be seen. A rather broad tail on the onset of this peak, is due to Co 4 N(111) (discussed later).…”

“…For R N 2 = 100%, CoN(200) peak gets broadened due to nanocrystallization. 34 To correlate N at.% with the structure of samples, secondary ion mass spectroscopy measurements were TABLE I. Parameters, crystal structure, grain size, lattice constant (a) and average magnetic moment (µ) per Co atom for Co-N thin film samples prepared for various R N 2 . For samples having hcp structure a = c is taken and cell parameter a = b = c/1.62.…”

Study of magnetic iron nitride thin films deposited by high power impulse magnetron sputtering

“…According to RAM, when particle size is above the ferromagnetic exchange length(L ex ), the H C increases with decreasing the particle size, and for the particle size below L ex , the H C decreases with decreasing the particle size. Generally, the value of L ex ∼30 nm, for pure iron [29,39] and expected to vary only slightly for iron nitride thin films. [40] In the present case observed variation in the H C does not correlate with the change in the crystallite size with increasing R N2 [see figure 2].…”

“…Phase formation of Fe-N thin films has been extensively studied by several co-workers using different thin film deposition techniques such as magnetron sputtering, [29,30] ion beam sputtering, [31,32] e-beam evaporation, [33] pulsed laser deposition, [34,35] as nitrogen partial pressure is increased in a physical vapor deposition method, different types of Fe-N phases are formed and they can be broadly classified as: nanocrys-…”

Tuning high frequency magnetic properties and damping of FeGa, FeGaN and FeGaB thin films

“…The results are observed in previous FeNiN films. 29 Moreover, as shown in the Fig. 1 (a), the (200) and (211) diffraction peaks disappear when the B atoms entered into the FeGa film, and the (110) peak changes to a weak hump which suggests an amorphous phase forms.…”