High-pressure phase transition and properties of spinelZnMn2O4

Abstract

X-ray photoelectron spectroscopy, magnetic measurements, and a single-crystal x-ray structure determination at normal pressure have shown that Jahn-Teller active manganese ions in ZnMn 2 O 4 are present in one valence state ͑III͒ on the octahedral sites of the spinel structure. The high-pressure behavior of ZnMn 2 O 4 was investigated up to 52 GPa using the energy-dispersive x-ray diffraction technique and synchrotron radiation. The structural first-order phase transition from the body-centered to primitive-tetragonal cell takes place at P c ϭ23 GPa. The high-pressure phase is metastable down to normal pressure. The c/a ratio reduces from 1.62 to 1.10 above P c and remains nearly pressure independent in the high-pressure phase. The transition is attributed to the changes in electron configuration of the Mn 3ϩ ions. According to the crystal field theory, the e g electron of octahedrally coordinated Mn 3ϩ is either in the d z 2 orbital or in the d x 2 Ϫy 2. In the first configuration the MnO 6 octahedron will be elongated and this is the case at normal pressure, while the second configuration gives the flattened octahedron. In the high-pressure phase some proportion of the e g electrons of the Mn 3ϩ ions is moved to the d x 2 Ϫy 2 level, which is revealed as an abrupt fall of observed magnitude of the distortion of the bulk crystal above P c . ͓S0163-1829͑99͒08341-1͔PHYSICAL REVIEW B

Lattice dynamics of ZnAl2O4 and ZnGa2O4 under high pressure

“…However, the theoretical study has suggested that a possible phase transition from the cubic spinel towards the tetragonal spinel structure can be explained by the presence of non-hydrostatic conditions. This transition had already been observed in ZnMn 2 O 4 [8] and NiMn 2 O 4 [9]. Figure 1 shows the unit cells of the cubic spinel, marokite, CaFe 2 O 4 and CaTi 2 O 4 phases.…”

Interface Double-Exchange Ferromagnetism in the Mn-Zn-O System: New Class of Biphase Magnetism

“…The simultaneous increase of the Zn x Mn 3ÿx O 4 phase and decrease of the ferromagnetic signal suggests that this phase is not responsible for the RT FM. Although there is some controversy about the magnetic properties of this spinel, it is well known that it exhibits paramagnetic behavior at RT [7]. For a further understanding, several samples in the Zn x Mn 3ÿx O 4 system have been prepared and characterized.…”

An efficient algorithm for finding the minimum energy path for cation migration in ionic materials

“…• Li in spinel LiTiS 2 (linear MEP); 51,52 • Zn in spinel ZnMn 2 O 4 (linear MEP); 23,53 • Zn in post-spinel ZnMn 2 O 4 (linear MEP); 54 • Li in olivine LiFePO 4 (curved MEP); [55][56][57][58][59] • Mg in δ-MgV 2 O 5 (curved MEP); 25,26,60,61 • Ca in layered CaMoO 3 (curved MEP). 62 To quantify the accuracy of the PathFinder algorithm in reproducing the geometry of the fully converged MEP, we define an error metric, shown schematically in Fig.…”