Brillouin Light Scattering studies of magnetic thin films and multilayers

crystal films. The films were grown on GaAs substrates and the BLS data gathered was analysed using derived expressions containing cubic and uniaxial anisotropy terms, the latter being derived here from first principals. 3. A series of FeCo alloy films deposited to thicknesses ranging from 46 A to 1000 A. The parameter of interest was the sample thickness below which the sample magnetization was found to be less that that of the bulk material. The BLS results were analysed using the Damon and Eshbach Surface mode expression. 4. The magnetic properties of an Fe/Cr trilayer wedge as a function of interlayer (Cr) spacer thickness. The transition from Antiferromagnetic to Ferromagnetic coupling was observed as function of Cr spacer thickness. BLS measurements at low and high field were correlated with features of the magnetization curves. 5. A series of 3 Co/Pt multilayers as a function of applied field. The results have yielded magnetization values for the films that are much lower than those of bulk Co. This was verified and explained as being due to the sample's high uniaxial anisotropy. The varied experiments discussed above have demonstrated the utility of BLS as an additional means of magnetic characterisation. Brillouin Light Scattering (BLS) is the process in which a high frequency photon is elastically scattered from a low frequency acoustic excitation. The scattered photon undergoes a change in frequency equal to that of the excitation. It has been shown that BLS is an extremely valuable technique for the characterisation of magnetic thin films. It can be used to determine, through suitable modelling, gyromagnetic ratio (gamma) saturation magnetization (4 pi M sub s), anisotropy properties and exchange parameters of magnetic samples. In principal, BLS can be used to determine any property that affects the spin wave dispersion relation of a sample. A BLS study of 5 series of samples is presented, each series having its own particular scientific interest, for example device applications or structural phenomena. These results were interpreted using appropriate theoretical dispersion relations. The BLS measurements were made on: 1. A series of five Ga-substituted YlG films (Y sub 3 Fe sub 5 sub - sub x Ga sub x O sub 1 sub 2 with 0<=x<=0.73). The exchange constant of each of the films was determined as a function of the Ga substitution variable following heat treatment of the samples. The effects of this heat treatment were studied in relation to substituted ion distribution. A paper on this work was presented at EMMA Zaragoza (1998) and published in the Journal of Magnetism and Magnetic Materials. A copy of this paper is included as an appendix. 2. A series of four MnSb singl