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M. LABEAU et al. 761Many details relating to the formation of the microdomains and the structural modifications at the domain boundaries remain unknown and further studies on this interesting material are warranted, using high-resolution electron microscopy as well as inelastic neutron diffraction. ReferencesALARIO-FRANCO, M. A., GREY, I. E., JOUBERT, J. C., VINCENT, H. & LABEAU, M. (1982). Acta Cryst. A38, 177-186. AbstractThe properties of Gaussian growth-disorder models are explored and their use for producing realizations of disordered lattices for optical transform analogue experiments is described. Use of Gaussian variables provides greater flexibility than previously described binary ones and in particular enables realizations to be produced in dimensions greater than two without restriction on the values of nearest-neighbour correlation coefficients. A method of converting Gaussian realizations to binary ones is also described.

The inverse susceptibility-temperature curves of Mn,Hgl-,Te (5 = 0.06, 0.11, 0.17, 0.235) showed a Curie-Weiss behaviour at high temperatures and a downward deviation at low temperatures. The paramagnetic Curie temperatures and effective numbers of magnetic carriers also deviated from a linear dependence on x a t low values of x. These results were explained in terms of a cluster model at low x values and a molecular field model a t high x.Die reziproken Suszeptibilitiits-Temperatur-Kurven von Mn,Hgl -,Te (x = 0,05 ; 0 , l l ; 0,17; 0,235) zeigen ein Curie-Weiss-Verhalten bei hohen Temperaturen und eine abwarts fallende Abweichung bei tiefen Temperaturen. Die paramagnetischen Curie-Temperaturen und die effektive Anzahl der magnetischen Triiger zeigen ebenfalls eine Abweichung von der linearen Abhangigkeit von z bei kleinen x-Werten. Diese Ergebnisse werden mit einem Cluster-Mode11 fur kleine z-Werte und einem Molekularfeld-Modell fur groBe z-Werte erklart.

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