Measurements of Elastic Constants in Thin Films of Colossal Magnetoresistance Material

Abstract

Measurements of elastic constants of strained 200 and 400 nm thin films, as well as unstrained samples, of the colossal magnetoresistance (CMR) material La0.67Ca0.33MnO3 are presented. Since the peak resistance temperature of a strained CMR film decreases as the film thickness decreases, it is of interest to see if features in the elastic constants, reflecting structural or magnetic changes, follow the peak resistance temperature. It is observed that features in the elastic constants appear not only at the peak resistance temperatures of the CMR samples, but also at a temperature about 17 K higher. A new technique, thin-film resonant ultrasound spectroscopy, was used to make the measurements.

Role of disorder in phase coexistence in manganites: Noise in layered films

“…In the fixed-volume case, phase coexistence regimes are of course inevitable. One can use data on the dependence of T C on pressure, 33 the elastic moduli in related bulk compounds 34 and in films, 35 the volume change at T C , 36 the entropy associated with the magnetic transition, 37 and the dependence of T C on substrate mismatch, 23 to make several estimates of the expected width of the coexistence region in a simple model, ignoring the anisotropy of the changes in lattice constants at the transition. The volume change data ͑0.08%͒ ͑Ref.…”

Resonant-ultrasound spectroscopy for studying annealing effect on elastic constant of thin film

“…RUS has been developed and advanced by Anderson et al [23], Ohno [24], Miglioiri et al [25], Ledbetter et al [26], and Maynard [27], and elastic properties of single crystal [28,29], piezoelectric material [30,31], composite [32], and thin films [33] have been studied. RUS is superior to other techniques because it is capable of determining anisotropic elastic constant and being unnecessary to grip the specimen.…”

Resonant ultrasound spectroscopy for investigation of thin surface coatings

“…By decreasing the thickness of one of the layers, such 'sandwich' obviously limits to a substrate-coating system; this idea was utilized by So et al [14], who used the concept outlined in [13] for modeling of free vibrations of a SrTiO 3 substrate coated by a thin magnetoresistant film.…”