Phase Separation Scenario for Manganese Oxides and Related Materials

Abstract

Recent computational studies of models for manganese oxides have revealed a rich phase diagram, which was not anticipated in early calculations in this context performed in the 1950s and 1960s. In particular, the transition between the antiferromagnetic insulator state of the hole-undoped limit and the ferromagnetic metal at finite hole density was found to occur through a mixed-phase process. When extended Coulomb interactions are included, a microscopically charged inhomogeneous state should be stabilized. These phase separation tendencies, also present at low electronic densities, influence the properties of the ferromagnetic region by increasing charge fluctuations. Experimental data reviewed here by applying several techniques for manganites and other materials are consistent with this scenario. Similarities with results previously discussed in the context of cuprates are clear from this analysis, although the phase segregation tendencies in manganites appear stronger.

The next 25 years of surface physics

“…Electronic phase separation in highly correlated systems is one of the currently hot subjects in CMP [8,[42][43][44][45][46][47]. Undoubtedly, the best known representative of this phenomena is ''stripes'' in the high temperature superconductors [8,44].…”

“…In this case, neutron scattering revealed the existence of correlated strips of spin and holes in the copper oxide superconductors [44]. This has led to what is referred to as ''stripology'', generating exciting speculation about the nature of these spin and electron inhomogeneous phases in highly correlated systems [42,43]. Recent electron microscopy and STM studies of the CMR perovskites show electronic phase separation on the $ lm scale.…”

Ferroelectric Field Effect Control of Magnetism in Multiferroic Heterostructures

“…The doped lanthanum manganites are complex oxides characterized by a strong interplay between charge, spin, and crystal lattice distortions, which is at the origin of the multifunctional behavior that is a hallmark of this class of compounds Moreo et al (1999); Tokura & Tomioka (1999). Examples of the rich electronic and magnetic behavior found in the doped lanthanum manganites include magnetic and charge-ordered states, colossal magnetoresistance (CMR), high spin polarizations, and various electron transport regimes.…”

Micro-Raman and magnetization studies of Nd1-xCaxMnO3phase transitions

“…The precursor effects expected in the low-doping regime are of great interest since they provide an insight to the physical parameters or mechanisms that play major roles even in the large-doping regime. While recent theoretical and experimental developments predict inhomogeneous ground state and phase separation [6], according to mean field theory the magnetic ground state corresponds to a canted antiferromagnetic homogeneous state at low-doping regime [7]. In the low-doping regime for Ca and Sr doped LaMnO 3 [8] puzzling ferromagnetic insulating states, that the double exchange described by Zener [1] could not explain, have been reported.…”