Local electronic states of Fe4N films revealed by x-ray absorption spectroscopy and x-ray magnetic circular dichroism

Abstract

We performed x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) measurements at Fe L2,3 and N K-edges for Fe4N epitaxial films grown by molecular beam epitaxy. In order to clarify the element specific local electronic structure of Fe4N, we compared experimentally obtained XAS and XMCD spectra with those simulated by a combination of a first-principles calculation and Fermi's golden rule. We revealed that the shoulders observed at Fe L2,3-edges in the XAS and XMCD spectra were due to the electric dipole transition from the Fe 2p core-level to the hybridization state generated by σ* anti-bonding between the orbitals of N 2p at the body-centered site and Fe 3d on the face-centered (II) sites. Thus, the observed shoulders were attributed to the local electronic structure of Fe atoms at II sites. As to the N K-edge, the line shape of the obtained spectra was explained by the dipole transition from the N 1s core-level to the hybridization state formed by π* and σ* anti-bondings between the Fe 3d and N 2p orbitals. This hybridization plays an important role in featuring the electronic structures and physical properties of Fe4N.

Effect of interfacial interdiffusion on magnetism in epitaxial Fe4N films on LaAlO3 substrates

“…A shoulder (marked by the ) can also be seen about 3 eV above the L 3 edge and is more pronounced in sample B grown using HiPIMS. It may be noted here that such shoulder has been observed in some metallic ferromagnetic systems and has been explained in terms of the unoccupied single-particle density of states [29]. Here, this feature ( ) can be attributed to the dipole transition from the Fe 2p core-level to the hybridized state σ * between Fe (II) sites [43] and N 2p orbitals [19,21,29].…”

“…However, to the best of our knowledge, experimentally the magnetic moment at the N site has only been studied by Ito et al using XMCD measurements, but a large discrepancy between the theoretically simulated and experimentally observed N K-edge spectra can also be seen there [29]. In the present case, as we have shown that the Fe 4 N sample grown using HiPIMS was superior and it will be interesting to inspect the electronic and magnetic behavior at Fe and N sites.…”

“…Moreover, different deposition methodology may also lead to different microstructure and hence different M s values in Fe 4 N thin film. Mostly, direct current magnetron sputtering (dcMS) [14][15][16][17][18] and molecular beam epitaxy (MBE) [19,[28][29][30][31] methods have been extensively used to prepare the Fe 4 N films, whereas a relatively new but very promising technique-high power impulse magnetron sputtering (HiPIMS)-has not yet been employed. There are several advantages inherent to the HiPIMS process over the conventional dcMS process such as improvement of the film quality by denser microstructure and enhanced adhesion etc.…”

Structural and magnetic properties of Co-N thin films deposited using magnetron sputtering at 523 K

“…In addition, the feature a ′ , a shoulder to feature a, shows a clear variation for samples deposited with or without nitrogen. This feature appears due to different chemical bonding at inequivalent 3d metal sites [27,29] and is a characteristic feature for anti-pervoskite type structures. We also notice that the intensity of feature a, a ′ and b is more (than pure Co) when nitrogen gas is used during sputtering.…”

“…A lot of theoretical [11,12,13,14,15] and experimental [16,17,18,19,20,21,22,23] reports are available on iron nitride (Fe-N) system. In a number of studies Fe 4 N thin films have been prepared and studied [16,17,18,19,20,21,22,23]. On the other hand, the Co-N system has not been explored as much.…”