Oxide electronics

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:

The distributions of surface oscillation and surface charges were probed within an interdigital transducer (IDT). The IDT was driven at a frequency of 39.5 MHz. The measurements with sub-μm spatial resolution were performed with a scanning acoustic force microscope. It utilizes the nonlinear interaction of the sample with the tip of a scanning force microscope. In the case of surface oscillation detection, this nonlinearity leads to a shift of the mean position of the cantilever due to varying oscillation amplitudes. The surface charges are mapped through the additional cantilever deflection caused by the attraction of the plates of the capacitor formed by the cantilever and the sample. Spatial distributions of the amplitude of surface oscillations and of surface charges at the end of a 39.5 MHz splitfinger IDT are presented. The obtained experimental results may lead to a deeper understanding in modelling of IDTs in the future.

Abstract:

We report about a new technique for the investigation of SAW fields within SAW devices reaching submicron lateral resolution. The scanning acoustic force microscope (SAFM) is based on a standard force microscope and utilizes the nonlinear force curve in the sense of a mechanical diode. Varying wave amplitudes therefore lead to different shifts of the cantilever's rest position. With SAFM we investigated SAW devices with center frequencies above 600 MHz. We found a local effect of massloading on the standing wave amplitude within IDTs. Furthermore, we measured the dynamic behavior of the IDT's wave pattern when sweeping the frequency.

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.