Extrinsic inhomogeneity effects in magnetic, transport and magnetoresistive properties of () crystal prepared by the floating-zone method

The dependence of percolation threshold on doping degree in La1−x(K, Ag)xMnO3 manganites

“…Granular (polycrystalline) manganites are the heterogeneous systems: each pellet should be considered as a grain consisting of a center with a certain T C and the same near surface layer depleted by the charge carriers [25]. This layer is magnetically and structurally heterogeneous; it has its own very fuzzy critical temperature considerably lower than T C .…”

Ferromagnetic domain structure ofLa0.78Ca0.22MnO3single crystals

“…Recently a double peak feature was also observed in optimally doped LCMO single crystals. 15 However, in single crystalline samples there are no grain boundaries and possible barriers for spin-polarized tunnelling may be associated with domain walls pinned to twin boundaries. 7 Twin domain boundaries in CMR manganites single crystals play a role similar to that of grain boundaries in polycrystalline samples.…”

“…7 Twin domain boundaries in CMR manganites single crystals play a role similar to that of grain boundaries in polycrystalline samples. 6,15 Due to strong band bending at the boundary the carrier concentration is depleted and the temperature of the local M-I transition is depressed. 14,15,16,17 The low temperature peak in the existing literature is thus interpreted as being due to local M-I transitions occurring at lower temperature than those in the sample bulk.…”

“…6,15 Due to strong band bending at the boundary the carrier concentration is depleted and the temperature of the local M-I transition is depressed. 14,15,16,17 The low temperature peak in the existing literature is thus interpreted as being due to local M-I transitions occurring at lower temperature than those in the sample bulk. 14,15,16,17 Note that the double peak resistivity structure can be observed only in samples with low specific resistance at low temperatures, such that relatively low second maximum is not obscured by other resistivity contributions which strongly increase with decreasing temperature.…”

“…15,34 Recently, high resolution X-ray diffraction and neutron powder diffraction structural investigation of low doped LCMO samples have established that for temperatures below x-dependent T JT the symmetry changes from orthorhombic P nma to monoclinic P 2 1 /c. 35 The transition was directly revealed through observations of splitting of (hk0) and (hkl) diffraction peaks, not allowed in the P nma space group.…”