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

Abstract

Epitaxial Fe 4 N thin films grown on LaAlO 3 (LAO) substrate using sputtering and molecular beam epitaxy techniques have been studied in this work. Within the sputtering process, films were grown with conventional direct current magnetron sputtering (dcMS) and using a high power impulse magnetron sputtering (HiPIMS) process. Surface morphology and depth profile studies on these samples reveal that HiPIMS deposited film has the lowest roughness, the highest packing density, and the sharpest interface. We found that the substrate-film interface and the microstructure play a vital role in affecting the electronic hybridization and magnetic properties of Fe 4 N films. La from the LAO substrate and Fe from the film interdiffuse and form an undesired interface. The magnetic moment (M s) was compared using bulk, element-specific and magnetic depth profiling techniques. We found that M s was the highest when the thickness of the interdiffused layer was lowest and such conditions can only be achieved in the HiPIMS grown samples. The presence of a small moment at the N site was also evidenced by element-specific x-ray circular dichroism measurement in the HiPIMS grown sample. A large variation in the M s values of Fe 4 N films found in the experimental works carried out so far could be due to such an interdiffused layer which is generally not expected to form in otherwise stable oxide substrate at a low substrate temperature ≈675 K. In addition, a consequence of substrate-film interdiffusion and microstructure resulted in the different kinds of magnetic anisotropies in Fe 4 N films grown using different techniques. A detailed investigation of the substrate-film interface and microstructure on the magnetization of Fe 4 N film is presented and discussed in this work.

Synthesis and Physical Properties of Antiperovskite CuNFe3 Thin Films via Solution Processing for Room Temperature Soft-Magnets

“…The M s per unit volume is 579 (~1.09 µB/Fe), 692 (~1.37 µB/Fe), and 950 emu/cm 3 (~1.79 µB/Fe), while the H c is 19.8, 16.7, and 3.7 Oe for the CNF/700, CNF/800, and CNF/900 thin films, respectively. It is observed that a higher M s is accompanied by a lower H c , which is the same as the previous reports [33][34][35][36]. The corresponding values are listed in Table 2.…”

Structure, Thermal Stability, and Magnetism of Ni4N Thin Films

“…The unique electronic and magnetic properties of the 3 d magnetic tetra transition metal nitrides M 4 N (M = Mn, Fe, Co, Ni) attract interest in realizing the development of magnetic memory and spintronic devices. [ 1–5 ] The ultrahigh tunnel magnetoresistance (TMR) recently reported in M 4 N family of compounds, indicate their feasibility as the electrode materials in magnetic tunnel junctions (MTJs). [ 3,5 ] M 4 N compounds have also been foreseen to serve as catalysts for photocatalytic water splitting reactions.…”

“…[ 1–5 ] The ultrahigh tunnel magnetoresistance (TMR) recently reported in M 4 N family of compounds, indicate their feasibility as the electrode materials in magnetic tunnel junctions (MTJs). [ 3,5 ] M 4 N compounds have also been foreseen to serve as catalysts for photocatalytic water splitting reactions. [ 6–8 ] Among M 4 N, the most significant research interest has been devoted to Fe 4 N due to its multifold magnetic merits.…”

Structural and magnetic properties of co-sputtered Fe0.8C0.2 thin films

“…An expansion in volume produces a higher density of states near the Fermi level due to contraction of d band (relative to Fe) and therefore results in higher M. The increase in M due to volume expansion is known as magnetovolume effect [7]. Experimentally, M of Fe 4 N has been achieved close to its theoretical values (≈2.4 μ B ) in several works [8][9][10][11]. Such enhancement in M with respect to pure Fe (M of Fe = 2.2 μ B ) make them very useful in various applications, e.g., spintronics, magnetic data storage devices [12], permanent magnets, spin-injection electrodes [5], etc.…”