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The principle of active microwave imagery is as follows: the medium and the object are traversed by an electromagnetic wave of known characteristics and the image of the object is then reconstituted from the scattered field measured beyond the object. Unfortunately the problem is ill-posed and the results are not unique. The analytical method uses the assumption div J=0; this assumption is discussed and compared with other methods and the results of numerical simulation are given. The maximum entropy method is used to obtain the image whose structure is the nearest figure. The images obtained by this method have a good accuracy and show proof of the high standing of this method of image reconstruction.

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Several publications have been devoted to the study of standing spin waves in thin ferromagnetic conducting plates. The exciting microwave field is very often considered as constant on the width of the plates, then propagation effects are disregarded. Here, on the contrary, it is shown that it is a complex electromagnetic problem in the most general case from the coupling of electromagnetic and spin waves. Thus it is possible to find theoretically the main experimental results obtained on thin nickel films, and particularly to indicate the effect, the sign, and the value of the surface anisotropy constant on each side of the plates.Plusieurs publications ont 6th consacrbes B I'btude des ondes de spin stationnaires dans des lames minces conductrices ferromagnbtiques. Le champ hyperfrkquence excitant est trhs souvent considbrb comme uniforme sur 1'8paisseur des lames, les phbnombnes de propagation sont ainsi nbgligbs. Nous montrons qu'il s'agit, au contraire, d'un problbme d'blectromagnbtisme tres blaborb que nous essayons de poser dans sa plus grande gbnbralitb B partir du couplage des ondes blectromagnbtiques et des ondes de spin. Nous avons ainsi la possibilitb de trouver thboriquement les principaux rbsultats expbrimentaux obtenus sur des lames de Nickel et de prbciser, en particulier, le rdle, le signe et la valeur des constantes d'anisotropie de surface sur chacune des faces des lames.

No abstract