Cycloidal phases

Fig. 42. Structural and magnetic phase diagram tor the Co Ni MnGe system. Tu is the temperature of the first-order structural transition, the Neel temperature, Tc the Curie temperature. Structures SS, simple spiral CS, cycloidal spiral FS ferromagnetic spiral (Zach et al. 1984, Niziol et al. 1982).

Cuboid and cycloid niobium monocarbide (NbC) whiskers, 0.1-2.0 pm in diameter and 5-100 pm in length, and having a square-shaped tip, were recently synthesized by heating mixtures of niobium oxide (Nb203) and carbon black at temperatures over 1100°C [38]. Silicon carbide nano-whiskers, 20-50 nm in diameter and 2-5 pm in length, were carbothermally synthesized by reducing ultrafine precipitated silica powders with ultrafine carbon black by microwave heating [29]. These processes proceed without addition of metal particle catalysts, and therefore by a VS phase transformation [14] [29] [38]. 

The main contribution of X-ray magnetic scattering to the study of Er has been to shed further light on the phases in the intermediate temperature interval between and Tc, and more recently to characterize the temperature dependence of the magnetic order parameter near 7. X-ray magnetic scattering has revealed a great wealth of new information on these intermediate phases that fits most easily with the cycloidal model. 

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