Ferromagnetic resonance linewidth and anisotropy dispersions in thin Fe films

In-plane ferromagnetic resonance (FMR) has been used to study the room-temp erature linewidth Delta H of single crystal Fe films grown by dc magnetron sputtering onto MgO(100) substrates. Several samples were grown with the fi lm thickness in the range 70 Angstrom < t(Fe) < 250 Angstrom. The measureme nts were carried out in the frequency range from 7.0 to 12.3 GHz. A phenome nological model for the FMR linewidth was developed that includes simultane ous effects due to intrinsic damping and angular dispersions of the cubic a nd uniaxial axes of anisotropy. These angular dispersions are found to be r esponsible for the relatively larger linewidths observed as a function of t he in-plane field direction with fixed frequency, and as a function of freq uency for the easy and hard directions as well. The behavior of the linewid th with the film thickness can be described by a sum of a constant volume t erm plus a term proportional to 1/t(Fe), representing the relaxation due to the misfit dislocations. (C) 1999 American Institute of Physics. [S0021-89 79(99)02009-5].