Surface composition and chemistry of evaporated Permalloy films observed by x−ray photoemission spectroscopy and by Auger electron spectroscopy

Abstract

Auger electron spectroscopy (AES) and x−ray photoemission spectroscopy (XPS) are addressed to the problem of characterizing the air−formed oxide layer on 50−2000−Å−thick Permalloy films. Ar+ ion sputter etching is employed to obtain an elemental profile with AES and a chemical profile with XPS. The films were prepared in a vacuum of 5×10−7 Torr and exposed to the laboratory environment for three weeks. The surface of these unprotected Permalloy films is found to have a composition and chemistry quite different from that of pure Permalloy. For thin films (50 Å) this abnormal region constitutes a sizeable portion of the film. A complex chemisorption layer is observed on top of a 12−Å oxide layer. The Fe−to−Ni ratio in the oxide layer is twice that of the film bulk and the concentration of oxidized Ni falls off faster with depth than that of oxidized Fe. A localized depletion layer of iron, approximately 12 Å thick, is observed between the oxide layer and bulk Permalloy which appears at a depth of 25 Å into the film. These results suggest a consistent although far more complex surface than that implied from previous investigations. The influence of this oxide on the low−temperature ferromagnetic resonance of these films is discussed in the preceding paper.

Magnetic properties of nanocrystalline γ-Fe–Ni–N nitride systems

“…The peaks in XPS spectra correspond to different chemical states of oxygen, nitrogen, iron and nickel atoms. The peak positions, peak widths and relative intensities are given in Table II 30 Therefore, a fraction of nickel in ␥-Fe 0.25 Ni 0.75 -N is found to be inactive in surface oxidation effects. Thus, the atmospheric oxidation of ␥-Fe 0.25 Ni 0.75 -N results from the formation of the complex oxynitride layer at the surface of the ultrafine nitride particles.…”

Relaxation mechanism in NiFe thin films driven by spin angular momentum absorption throughout the antiferromagnetic phase transition in native surface oxides

“…For example CoFe alloys were recently theoretically predicted [12] and experimentally demonstrated [13] to display ultra-low damping which was previously believed to be unachievable in metallic ferromagnets. In this article, inspired by recent theoretical and experimental findings on spin-pumping [14][15][16][17][18][19], we chose to investigate Permalloy (NiFe) in an attempt to determine the incompletely-understood origin of their non-monotonous temperature-dependence of ferromagnetic damping [20][21][22][23][24][25]. More specifically, typical 3d transition metals (Co, Ni, Fe) and associated alloys (including NiFe) frequently show a minimum in their temperature-dependence of damping [26,27].…”

“…In fact, if not protected from oxidation due to exposure to air, a few monolayers of the NiFe layer will naturally oxidize to form a passivating oxide layer (NiFeOx). This layer contains a complex mixture of NiO and FeO antiferromagnetic alloys with variable stoichiometry gradients [25]. In this context, the potential influence of relaxation of interface paramagnetic impurities in bilayers where a ferromagnet is exchange-biased to an antiferromagnet was considered in several studies [31][32][33][34].…”

Magnetic properties of double exchange biased diluted magnetic alloy/ferromagnet/antiferromagnet trilayers

“…After the deposition of the CuMn/Py bilayers, the samples were exposed to atmospheric pressure at room temperature. As it as been unambiguously demonstrated, the thermal oxidation of the external Py film exposed to the laboratory environment produces an α-Fe 2 O 3 surface AF layer [25,26,27,28,29]. Indeed, according to the Fe-O phase diagram [30], α-Fe 2 O 3 is the stable phase at room temperature and atmospheric pressure.…”