We used low-temperature synchrotron x-ray diffraction to investigate the structural phase transitions of Fe${}_{1+y}$Te in the vicinity of a tricitical point in the phase diagram. A detailed analysis of the powder diffraction patterns and temperature dependence of the peak widths in Fe${}_{1+y}$Te showed that two-step structural and magnetic phase transitions occur within the compositional range $0.11$\le${}y$\le${}0.13$. The phase transitions are sluggish, indicating a strong competition between the orthorhombic and the monoclinic phases. We combine high-resolution diffraction experiments with specific heat, resistivity, and magnetization measurements and present a revised temperature-composition phase diagram for Fe${}_{1+y}$Te.

The morphogenesis of hierarchically ordered, spherical aggregates of fluorapatite–gelatine-nanocomposites starts with elongated hexagonal prismatic seeds, followed by fractal branchings and the development of growing dumbbell states. The general principles of this dramatic process of self-organisation are not yet known but should be laid out already in the real structure of the central seed (P. Simon, W. Carrillo-Cabrera, P. Formanek, C. Göbel, D. Geiger, R. Ramlau, H. Tlatlik, J. Buder and R. Kniep, J. Mater. Chem., 2004, 14, 2218, ). Here we describe the structure and inner architecture of the fluorapatite composite seeds which consist of self-similar nano-subunits nucleated by gelatine macromelecules. Although grown without any cell activities, the biomimetic composite closely resembles natural biomaterials based on interactions between collagen and apatite.