Formation dynamics of FeN thin films on Cu(100) Dodi Heryadi1 and Udo Schwingenschlögl2 1Supercomputing Laboratory, King Abdullah University of Science and Technology (KAUST)   2Physical Science & Engineering, King Abdullah University of Science and Technology (KAUST)

Abstract To investigate the structural and magnetic properties of thin films of FeN we have performed ab-initio molecular dynamics simulations of their formation on Cu(100) substrates. The iron nitride layers exhibit a p4gm(2x2) reconstruction and order ferromagnetically in agreement with experiment. We establish the dynamics and time scale of the film formation as a function of the film thickness. The process can be split in two phases: formation of almost flat FeN layers and subsequent optimization of the distance to the substrate. Our calculated magnetic moments are 1.67 B, 2.14 B, and 2.21 B for one, two, and three monolayers of iron nitride. We find that the magnetization trend follows the experimental behavior while the magnitudes of the magnetic moments differ considerably, which is indicative of structural imperfections of the samples used in the experiment. KAUST King Abdullah University of Science and Technology

initial structures to simulate the formations of 1-3 ML of FeN Side views (a, c, and e) and top views (b, d, and f) of the initial structure to simulate the formations of 1 ML (a and b), 2 ML (c and d), and 3 ML (e and f) of iron nitride. Fe, N, and Cu atoms are represented by blue, purple, and green spheres. KAUST King Abdullah University of Science and Technology

equilibrium structures of 1-3 ML of iron nitrides on Cu(100) Side views (a, c, and e) and top views (b, d, and f) of snapshots of the equilibrium structures of 1 ML (a and b), 2 ML (c and d), and 3 ML (e and f) of iron nitride after 6 ps of simulation time. Fe, N, and Cu atoms are represented by blue, purple, and green spheres, respectively. KAUST King Abdullah University of Science and Technology

evolution of geometrical parameters for the 1 ML simulation Evolution of geometrical parameters for the 1 ML simulation: atomic distances (b and c) and bond angles (d). The atom labels are identified in (a). KAUST King Abdullah University of Science and Technology

evolution of geometrical parameters for the 2 ML simulation Evolution of geometrical parameters for the 2 ML simulation: atomic distances (b and c) and bond angles (d). The atom labels are identified in (a). KAUST King Abdullah University of Science and Technology

evolution of geometrical parameters for the 3 ML simulation Evolution of geometrical parameters for the 3 ML simulation: atomic distances (b and c) and bond angles (d). The atom labels are identified in (a). KAUST King Abdullah University of Science and Technology

geometries and magnetizations compared to experiment Table 1: Distances (in Å) obtained for simulations of 1 ML, 2 ML, and 3 ML of iron nitride compared to the experiment   Fe-Fe Fe-N 1 ML 2.52 1.98 2 ML 2.54 1.94 3 ML 2.60 Experiment for -Fe4N [1] 2.68 1.90 1. H. Jacobs, D. R. Rechenbach, and U. Zachwieja, J. Alloys Compounds 227, 10 (1995). Table 2: Magnetizations (B) obtained from ab-initio molecular dynamics simulations and XMCD measurements   This work Experiment [2] 1 ML 1.67 0.73 2 ML 2.14 1.47 3 ML 2.21 2.17 2. Y. Takagi, K. Isami, I. Yamamoto, T. Nakagawa, and T. Yokoyama, Phys. Rev. B 81, 035422 (2010). KAUST King Abdullah University of Science and Technology