Correlation between magnetic interactions and domain structure in A1 FePt ferromagnetic thin films

N. ALVAREZ; E. SALLICA LEVA; R. C. VALANTE; M. VÁSQUEZ MANSILLA; J. GÓMEZ; J. MILANO; A. BUTERA

JOURNAL OF APPLIED PHYSICS

AMER INST PHYSICS

Lugar: New York; Año: 2014 vol. 115 p. 83907 - 83917

0021-8979

We have investigated the relationship between the domain structure and the magnetic interactions in a series of FePt ferromagnetic thin films of varying thickness. As-made films grow in the magnetically soft and chemically disordered A1 phase that may have two distinct domain structures. Above a critical thickness d_cr~30 nm the presence of an out of plane anisotropy induces the formation of stripes, while for d thinner than d_cr planar domains occur. Magnetic interactions have been characterized using the well known DCD-IRM remanence protocols, DM plots, and magnetic viscosity measurements. We have observed a strong correlation between the domain configuration and the sign of the magnetic interactions. Planar domains are associated with positive exchange-like interactions, while stripe domains have a strong negative dipolar-like contribution. In this last case we have found a close correlation between the interaction parameter and the surface dipolar energy of the stripe domain structure. Using time dependent magnetic viscosity measurements, we have also estimated an average activation volume for magnetic reversal, V_ac ~ 1.37x10^4 nm^3, which is approximately independent of the film thickness or the stripe period.