Nanoscale phase separation in La_0.7Ca_0.3MnO₃films: evidence for texture-driven optical anisotropy

Abstract

The IR optical absorption (0.1 eV <hω < 1.5 eV) in the La0.7Ca0.3M nO3 films on LaAlO3 substrate exhibits the drastic temperature evolution of the spectral weight evidencing the insulator to metal transition. Single crystal films were found to reveal strong linear dichroism with anomalous spectral oscillations and fairly weak temperature dependence. Starting from the concept of phase separation, we develop the effective medium model to account for these effects. The optical anisotropy of the films is attributed to the texturization of the ellipsoidal inclusions of the quasimetal phase caused by a mismatch of the film and substrate and the twin texture of the latter.

Low field magnetotransport in manganites

“…Several other experimental techniques, e.g. EXAFS [193], PDF (x-ray as well as neutron) [194], neutron scattering [195], Raman scattering [196], Mossbauer spectroscopy [197], muon spin relaxation [198], infrared reflectivity [199], photoabsorption spectroscopy [200], isotope effect [201], specific heat [202], thermal expansion measurements [203], optical studies [204], internal friction [205] and others, give strong evidence of phase separation in a variety of manganite systems. Further evidence of phase separation in manganites comes from inhomogeneous conductivity in the vicinity of the insulator-metal transition for the noise characteristics of film and single-crystal samples.…”

Features of absorption of thin films La-=SUB=-0.69-=/SUB=-Ba-=SUB=-0.31-=/SUB=-MnO-=SUB=-3-delta-=/SUB=- obtained using the method of pulsed laser deposition

“…The band at 2 µm was observed by us earlier in the spectra t/t 0 of other manganite films, but its nature was not discussed in detail. It can be assumed, that in this case there is a superposition of two bands: a band associated with transitions in electron clusters, and a band associated with the excitation of surface or bulk plasmons, as in [37], or various geometric resonances (resonances Mi) at the boundary of inhomogeneities in the phase separation region, as in [38]. It is important to note, that the temperature dependences t/t 0 at wavelengths 2 and 6 µm coincide (Fig.…”

Особенности поглощения тонких пленок La-=SUB=-0.69-=/SUB=-Ba-=SUB=-0.31-=/SUB=-MnO-=SUB=-3-delta-=/SUB=-, полученных методом импульсного лазерного осаждения

“…Полоса при 2 µm наблюдалась нами ранее в спектрах t/t 0 других пленок манганитов, однако детально ее природа не обсуждалась. Можно предположить, что в данном случае имеет место наложение двух полос: полосы, связанной с переходами в электронных кластерах, и полосы, связанной с возбуждением поверхностных или объемных плазмонов, как в [37], или различных геометрических резонансов (резонансов Ми) на границе неоднородностей в области фазового расслоения, как в работе [38]. Важно заметить, Оптика и спектроскопия, 2022, том 130, вып.…”