Search

Yttrium-iron-garnet (YIG) films for magneto-optical applications are made by liquid phase epitaxy (LPE) from a melt containing Pb ions. In the course of annealing procedures Pb segregates on the surface of the YIG films. The evidence for and the temperature dependence of the segregation is studied by low energy ion scattering (ISS).

The weak ferromagnet FeBO3 exhibits a strong dependence of the transverse sound velocity on the external magnetic field. This dependence has been measured for phonons up to the GHz region. The results can be explained satisfactorily by the interaction of the phonon and magnon dispersion branches.

The radial oscillation of bubble lattices in LPE garnet films has been measured as a function of static fields applied perpendicular to the film or in the film plane, using a simple RF technique. While the dependence of the measured resonance frequency on the normal field can be described by theory, the measured frequency increases more rapidly with the in-plane field than calculated; this discrepancy is probably due to an incorrect theoretical dependence of the wall mass on the in-plane field.

Magnetic bubble films exhibit a number of ferrimagnetic resonance modes due to the spatial variation of the anisotropy. The resonance frequencies have been measured as a function of the applied bias fieldH 0. In the lower field range the magnetization of the transient layer, which has negative anisotropy, is not yet parallel toH 0. In this range the resonance frequencies are shifted to higher values due to pinning effects. In films grown by the vertical dipping method an additional layer on top of the transient layer is observed within which the magnetization rotates from the direction in the transient layer to that of the bulk of the film. In films grown by horizontal dipping no such layer could be detected. Each ferrimagnetic resonance mode excites transverse elastic waves in the film due to the magnetoelastic interaction and thus gives rise to elastic resonances of the whole crystal, film and substrate. These elastic resonances lead to a fine-structure of the ferrimagnetic resonances. The observed fine-structure vanishes periodically with frequency and from this behaviour the thickness of the magnetic film and of the transient layer has been determined.

Magnetoelastic excitations with a fine structure in the 50kHz range have been observed in the study of the domain wall resonance (DWR) in magnetic garnet thin films. DWR excites standing transverse elastic waves which have a resonance frequency given by f= nv 2d , where f is the frequency, n is an integer, v=3.5×10 5 cm/sec is the transversal velocity of the elastic wave, and d=0.05 cm is thickness of the film/substrate system. A fine structure associated with each of these modes has been identified as due to two dimensional bulk elastic waves by using a set of parallel microstrip lines. The dispersion relation of these elastic waves is ω 2 = v 2 ( k 2 1 + k 2 2 ), where ω is the radial frequency, k 1 and k 2 are the wave vectors in the orientation perpendicular and parallel to the sample surface respectively. In the case of k 1 ⪢k 2 , f= f 0 +v 2 k 2 2 f 0 , where f 0 is the resonance when k 2 =0. The experimental results are in excellent agreement with this model. A linear dispersion, observed when using a shorted slot-line structure, is understood as the excitation of three dimensional modes due to the complex structure of the slot-line and the sample geometry.

A study on the horizontally LPE-grown La, Ga: YIG films is presented. With the spin wave resonance technique the ratio of the saturation magnetizations of the bulk and transient layer has been measured. The average saturation magnetization was determined by means of a vibrating sample magnetometer and the Ga concentration by x-ray fluorescence analysis. These data are compared with the growth rates of both the transient and the bulk layer. A systematic dependence of the magnetization on the growth rate is found.

The infrared absorption of H-ions in LiF and H- and D-ions in NaF has been measured. The energetic positions of the local modes in NaF:D- and LiF:H- allow 2-phonon decay processes as indicated by the variation of the absorption bandwidth at low temperatures. In NaF side bands have been observed.