Uncorrelated and correlated nanoscale lattice distortions in the paramagnetic phase of magnetoresistive manganites

Abstract

Neutron scattering measurements on a magnetoresistive manganite La${}_{0.75}$(Ca${}_{0.45}$Sr${}_{0.55}$)${}_{0.25}$MnO${}_3$ show that uncorrelated dynamic polaronic lattice distortions are present in both the orthorhombic (O) and rhombohedral (R) paramagnetic phases. The uncorrelated distortions do not exhibit any significant anomaly at the O-to-R transition. Thus, both the paramagnetic phases are inhomogeneous on the nanometer scale, as confirmed further by strong damping of the acoustic phonons and by the anomalous Debye-Waller factors in these phases. In contrast, recent x-ray measurements and our neutron data show that polaronic correlations are present only in the O phase. In optimally doped manganites, the R phase is metallic, while the O paramagnetic state is insulating (or semiconducting). These measurements therefore strongly suggest that the {\it correlated} lattice distortions are primarily responsible for the insulating character of the paramagnetic state in magnetoresistive manganites.

arXiv comment10 pages, 8 figures embedded

References in corpus (18)

• Double Exchange Alone Does Not Explain the Resistivity of $L{a}_{1-x}S{r}_{x}Mn{O}_3$
• Dynamic Jahn-Teller Effect and Colossal Magnetoresistance in $L{a}_{1-x}{A}_{x}Mn{O}_3$
• Hall-Effect Sign Anomaly and Small-Polaronic Conduction in (La_{1-x}Gd_x)_{0.67}Ca_{0.33}MnO_3
• Optical Conductivity in Mott-Hubbard Systems
• Charge Ordering and Polaron Formation in the Magnetoresistive Oxide La0.7Ca0.3MnO3
• Relevance of Cooperative Lattice Effects and Correlated Disorder in Phase-Separation Theories for CMR Manganites
• Short-range polaron correlations in the ferromagnetic La(1-x)Ca(x)MnO(3)
• Thermal/Electronic Transport Properties and Two-Phase Mixtures in La_{5/8-x}Pr_{x}Ca_{3/8}MnO_{3}
• Charge melting and polaron collapse in $L{a}_{1.2}S{r}_{1.8}M{n}_2{O}_7$
• Soft Phonon Anomalies in the Relaxor Ferroelectric Pb(Zn_1/3Nb_2/3)_0.92Ti_0.08O_3
• Glass Transition in the Polaron Dynamics of CMR Manganites
• Direct Observation of High-Temperature Polaronic Behavior In Colossal Magnetoresistive Manganites
• Why stripes? Spontaneous formation of inhomogeneous structures due to elastic interactions
• Anomalous transverse acoustic phonon broadening in the relaxor ferroelectric Pb(Mg_1/3Nb_2/3)O_3
• Correlated Polarons in Dissimilar Perovskite Manganites
• Average Lattice Symmetry and Nanoscale Structural Correlations in Magnetoresistive Manganites
• Common features of nanoscale structural correlations in magnetoresistive manganites with ferromagnetic low-temperature state
• Influence of the cooperative Jahn-Teller effect on the transport- and magnetic properties of La_{7/8}Sr_{1/8}MnO_3 single crystals

Cited by in corpus (7)

• Spontaneous magnetization above $T_C$ in polycrystalline La${}_{0.7}$Ca${}_{0.3}$MnO${}_3$ and La${}_{0.7}$Ba${}_{0.3}$MnO${}_3$
• Percolative phase transition on ferromagnetic insulator manganites: uncorrelated to correlated polaron clusters
• Direct imaging of lattice strain-induced stripe phases in an optimally-doped manganite
• Evidence of ferromagnetic short-range correlations in cubic La1-xSrxMnO3-δ (x=0.80, 0.85) above antiferromagnetic ordering
• Non percolative nature of the metal-insulator transition and persistence of local Jahn-Teller distortions in the rhombohedral regime of La${}_{1-x}$Ca${}_x$MnO${}_3$
• Mesoscopic transport in ultrathin films of La${}_{0.67}$Ca${}_{0.33}$MnO${}_3$
• Damping and softening of transverse acoustic phonons in colossal magnetoresistive La${}_{0.7}$Ca${}_{0.3}$MnO${}_3$ and La${}_{0.7}$Sr${}_{0.3}$MnO${}_3$