Size and nitrogen catalytic effects on the magnetic properties of Fe thin films

The effects of physical size reduction and catalytic nitridation on the ferromagnetic behavior of Fe films were investigated using three approaches: (i) a theoretical study was conducted that involved incorporating the bond-orderlength-strength (BOLS) and bond-band-barrier (BBB) correlations [C.Q. Sun, Prog.Mater.Sci.48(6), 521 (2003)] in the Ising model premise and Brillouin functions to predict the magnetic performance at different temperatures; (ii) Monte Carlo simulations were carried out on the spin system with various cluster sizes and geometric shapes to verify the BOLS predictions; and (iii) nickel, iron, and iron nitride films were deposited using the filtered cathodic vacuum arc technique and were characterized to confirm the predictions and Monte Carlo simulations.It was found that when a solid (particle or film) forms at a nanometer scale, the effect of atomic coordination number (CN) imperfection and the following effect on the bond-length-strength dominate, which localize the charges that contribute to the angular momentum (J) and hence the magnetic moment (µ) of the system.The CN imperfection also affects the atomic cohesion, or the spinspin exchange interaction, of the lower-coordinated atoms, which determine the phase stability, or Curie temperature (T C ) suppression.The competition between charge localization and atomic cohesive energy reduction determines the magnetic behavior of a nanosolid at various temperatures.The coercivity (H C ), however, increases with the increase of size due to the rise of intergrain interaction.Understanding of the size-induced phase stability was extended to