Professor Paolo G. Radaelli OSI

Abstract:

The magnetic properties of La1-σMnO3 depend on the relative concentration of Mn+4/Mn+3 introduced by vacancies on La sites. Neutron diffraction, magnetization, AC susceptibility and heat capacity measurements have been performed on a powdered sample annealed in Argon. At low temperature the spins are canted; a phase transition occurs at 117 K. These data are compared with those of a sample annealed in air which shows a ferromagnetic transition at 245 K.

Abstract:

Neutron powder diffraction is used to determine the crystal structure of LiCD3COO · 2D2O at 293 and 1.5 K. Lithium acetate dihydrate crystallizes in the Cmmm space group in the room-temperature phase with a = 6.82082(9) Å, b = 10.88842(12) Å, c = 6.59911(7) Å, and Z = 4. The CH3 groups are dynamically disordered, and there are short H bonds between the water molecules and the acetate oxygen atoms. There is a phase transition to a low-temperature modification which has the space group Pman with a = 6.70246(7) Å, b = 10.87932(11) Å, c = 6.56999(7) Å, and Z = 4. The CH3 groups are ordered in this phase, but have large thermal ellipsoids even at 1.5 K. The H atoms of the water molecules also have large thermal ellipsoids even at 1.5 K, but the CH3 group tunneling spectrum shows no evidence for coupling with the motions of the water molecules. © 1996 Academic Press, Inc.