For appropriate values of perpendicular and in-plane magnetic fields, Hn and Hp, respectively, domain walls in (210) garnet films exhibit zig-zag and sinusoidal distortions along their lengths. Microdeformations of domain walls (DW) near these “instability loss lines”1 in the Hn, Hp plane were investigated in [1̄20]-oriented stripe domain structures by a dark-field magneto-optical technique. Changes of brightness and contrast of the image along and across the DW occur in response to an in-plane field Hp. Figure 1 shows a stripe domain structure with Hp=120 Oe along [001]. The analysis of the images2 confirms the presence of alternating DW parts inclined at angles ±α of about 3°–5° from the film normal. The domain-wall displacement varies through the film thickness as the result of the DW being pinned to the transitional level of the film–substrate interface. In the completely aligned stripe array, in-phase microdeformations have been observed for neighboring domain walls. With an increase of Hp, the DW parts with one direction of tilt are lengthened and the walls are reoriented from the [1̄20] to the [1̄21̄] direction. These results provide information on the spatial configuration of the deformed DW and give the possibility to create a more precise model of the domain and the domain wall in (210) garnet films.
For the experiments we used garnet films of composition (BiLuh(FeGa)S012 grown on (GdCa}J(GaMgZr)sOI2 and Gd3GaS0 1 2 substrates. Deviation of the crystallographic axis {21O} from the the film normal was less than 1°. Domain nucleation fields (Hp,Hn)nuc (H p is the in-plane field, Hn is the perpendicular one), were measured for different azimuthal angle cj> of Hp relative to the {120} axis by observation of the jump of the magnetization from the magneti cally saturated state. From the dependence of Hn on Hp for different cj> (Fig. 1), we have deter mined the easy axis (EA). From the comparison of these results with data from X-ray measure ments we have found that the EA of the samples investigated is situated close to the (001) plane and inclined from film normal n at an angle eo towards the {120} axis (Fig. 2.) The values of eo calcula � d from the susceptibility ratio XnnlXnp = tan eo (evaluated for cj> = 0, i.e. Hp is directed along {I20} ) are 9°, 20°,29°, and 30° for different samples.For fields Hn > 41tMs, which support the saturated state with critical field Hp in accordance with Stoner-Wohlfarth theory, nucleation takes place by nonreversible rotation of Ms. For cj> == ±TCI2, two directions of rotation are possible. The threshold values Hn and Hp depend on the uniaxial anisotropy field. 60 40 20 'V III 0 0
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