A SPIN-WAVE RESONANCE STUDY ON REENTRANT NI77MN23 THIN-FILMS

The magnetic properties of thin (300 Angstrom) reentrant Ni77Mn23 film s grown on a quartz substrate using the electron beam evaporation tech nique have been investigated. The spin-wave resonance (SWR) technique has been used to study the exchange parameter D and magnetic anisotrop ies as a function of temperature between 4 and 300 K. The SWR spectra exhibit directional character upon cooling the sample in an external f ield H-c, which is a sign of a spin-glass property. At higher temperat ures, in addition to the dominant surface SWR mode, there is a much we aker bulk mode on the lower field side. Using a uniaxial surface and e ffective bulk anisotropy together we simulated the experimental spectr a and deduced the surface anisotropy and magnetic stiffness parameters as a function of temperature. The sample shows an easy plane surface anisotropy. Both the exchange and anisotropy parameters increase when the temperature is in the spin-glass regime. Furthermore, the surface anisotropy energy dominates the overall magnetic behavior of this syst em.