Magnetic anisotropy energy as a function of temperature in tetragonal Ni films and Fe superlattices

The magnetic anisotropy energy (MAE) in FCT Ni(0 0 1) single crystals and i n BCT Fe/V(0 0 1) superlattices is determined by ferromagnetic resonance. S econd- and fourth-order anisotropy constants K-2, K-4\\ and K-4 perpendicul ar to are determined as a function of temperature. We find that the MAE is by orders of magnitude enhanced due to the tetragonal distortion. The fourt h-order anisotropy constants K-4\\ and K-4 perpendicular to are in general not negligible and can be as large as 50% of K-2. All constants show differ ent temperature dependencies. It is shown that this complete determination of MAE as a function of temperature provides a quantitative understanding o f the unconventional spin reorientation in Ni/Cu(0 0 1). Extrapolation of t he experimental K-i to low temperature allows a comparison with first princ iples calculations at T = 0 K. (C) 1999 Elsevier Science B.V. All rights re served.