Optical phase diagram of perovskite-type colossal magnetoresistance manganites with near-half doping

Abstract

We present a systematic optical study for a bandwidth-controlled series of nearly half doped colossal magnetoresistive manganites RE${}_{0.55}$AE${}_{0.45}$MnO${}_3$ (RE and AE being rare earth and alkaline earth ions, respectively) under the presence of quenched disorder over a broad temperature region $T=10-800$ K. The ground state of the compounds ranges from the charge and orbital ordered insulator through the spin glass to the ferromagnetic metal. The enhanced phase fluctuations, namely the short-range charge and orbital correlations dominate the paramagnetic region of the phase diagram above all the ground-state phases. This paramagnetic region is characterized by a full-gap to pseudo-gap crossover towards elevated temperatures where a broad low-energy electronic structure appears in the conductivity spectra over a large variation of the bandwidth. This pseudo-gap state with local correlations is robust against thermal fluctuations at least up to T=800 K. For small bandwidth the onset of the long-range charge order is accompanied by an instantaneous increase of the gap. The emergence of the ferromagnetic state is manifested in the optical spectra as a first-order insulator to metal transition for compounds with moderate bandwidth while it becomes a second-order transition on the larger bandwidth side. Unusually large scattering rate of the metallic carriers is observed in the ferromagnetic state which is attributed to orbital correlation with probably rod-like ($3z^2-r^2$-like) character.

References in corpus (6)

• Competing Orders and Disorder-induced Insulator to Metal Transition in Manganites
• Modelling colossal magnetoresistance manganites
• Understanding the insulating phase in CMR manganites: Shortening of the Jahn-Teller long-bond across the phase diagram of La_{1-x} Ca_x Mn O_3
• Colossal magnetocapacitance and scale-invariant dielectric response in phase-separated manganites
• Isosbestic points in the spectral function of correlated electrons
• Local distortion of MnO${}_6$ octahedron in La${}_{1-x}$Sr${}_x$MnO${}_{3+\delta }$ (x = 0.1 to 0.9): an EXAFS study

Cited by in corpus (2)

• Multicritical end-point of the first-order ferromagnetic transition in colossal magnetoresistive manganites
• Infrared spectroscopic studies of the topological properties in CaMnSb2