The high-frequency properties of La0.67Ca0.33MnO3 [LCMO(113)] and La0.67Sr1.33MnO4 [LSMO(214)] thin films were investigated by complex impedance spectra (CIS) at various temperatures. The CIS were then analyzed by using an equivalent circuit model to determine the correlation of the magnetic phase transition to the dielectric and transport properties. The dielectric properties of both systems are insensitive to temperature, revealing that the dielectric behavior is independent of magnetic phase transition but strongly associated with the transport properties. The results provide insight into dielectric variation during the phase transition from a ferromagnetic metallic phase and/or an antiferromagnetic insulating phase to a paramagnetic insulating phase.
A brief review of established methods shows that only with the Berthelot technique is it possible to see a finite volume of liquid in sustained mechanical tension. A short discussion of the practice and theory reveals two uncertainties with the conventional technique : that of the determination of a true filling temperature, and the influence of compliance by the glass on the tension developed. A description is then given of a modified apparatus with which these difficulties do not arise. The tube is formed into a coil which deflects sufficiently to indicate internal pressure or tension, and by monitoring these deflections with a distance meter a record of pressure/ tension against temperature can be made. The course of a typical run is shown from which the excess pressure, filling temperature and limiting tension may all be estimated with much greater precision than befoie. The orders of magnitude of the results obtained are indicated, and a possible influence of non-uniform gaseous supersaturation is suggested.
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