Enhancement of the Magnetotransport Behavior in a Phase-Separated LaAgCaMnO₃ Polycrystalline: Unraveling the Role of a Multi-Double-Exchange Mechanism

Abstract

Manganese-based perovskite oxides have attracted much attention since the phenomenon of colossal magnetoresistance (CMR) was revived, where the magnetoresistance (MR) can attend higher orders of magnitude larger than that typically found in other types of materials. While trying to understand the mechanism behind CMR, morphostructural, magnetoelectrical, and theoretical studies have been performed on the La 0.4 Ag 0.2 Ca 0.4 MnO 3 (LACMO) sample. An orthorhombic-shaped singlephase LACMO sample with size distribution D SEM = 2.5 μm was synthesized using a conventional sol−gel chemical method. The mixed valence states of different chemical elements were revealed by X-ray photoemission spectroscopy. The results of thermal dependence of magnetization were obtained according to the zero field cooled−field cooled cooling−field cooled warming protocols using a superconducting quantum interference device magnetometer. The phase separation (PS) phenomenon was observed because of the competition between the superexchange and the double-exchange (DE) mechanisms within the same material. Field dependence of magnetization at varying temperatures and in cooling−warming processes has also been reported and discussed in this paper. The MR value was found to be 99% under an applied field of 2 T. In essence, the reported CMR arises from the metal−insulator phase transition T ρ = 64 K, which accompanies the transition from an insulator state to a metallic state. Not only the large CMR value was noted in our sample, but also the high obtained value of the temperature coefficient of resistivity of 69% at 123 K in zero field has also been reported. The obtained CMR values are the result of PS and multi-DE phenomenon. The latter proved to be directly correlated with the improved magnetotransport properties because an additional hopping mechanism is provided by an interstitially filled Mn 2+ ion, which is electronically involved in the conduction mechanism, showing an unconventional behavior in the transport properties of manganite.

Magnetic effect and chemical distribution study of LCMNO3 perovskite by photoelectron spectroscopy

“…Phase Mn 3 O 4 (I41/amd) a (Å) and 3d3/2 components as an effect of electron transfer from the oxygen valence band into the empty La4f states [38]. As evidenced in various La-based perovskites [3,39,40], the ground state for trivalent lanthanum ions is described as 3d 9 4f°L, where L denotes oxygen ligand. After the photoionization, there are two possible final states, 3d 9 4f 0 L as the lower binding (LBE) peak and 3d 9 4f 1 L as the higher binding energy (HBE) peak, both noted for two 3d species.…”

“…Manganite, manganese-based perovskites with the general formula R 1−x A x MnO 3 (R-Trivalent rare earth; A-divalent ion), have piqued the interest of researchers because of their massive magnetoresistance, charge ordering (CO), orbital ordering (OO), phase separation, and spin-glass behavior [1][2][3][4][5][6][7][8]. These features may be controlled by varying the type and concentration of trivalent rare-earth or divalent alkaline-earth cations, which influence crystal structure deformation and e .g.…”

Understanding the charge carriers dynamics in the La0.55Ca0.45Mn0.8Nb0.2O3 perovskite: scaling of electrical conductivity spectra

“…Both lines are standard for manganites, where the super-exchange and double-exchange interactions are realized. 37 Such a higher parameter may point to the partial origin of Mn 3+ ions from octahedral sites of Mn 3 O 4 . Similarly, the third noted doublet assigned to Mn 2+ states (Δ E = 11.3 eV), may probably originate from the tetrahedral site impurity of the Mn 3 O 4 phase.…”

La0.6X0.1Te0.3MnO3 system with significant refrigerant capacity at low magnetic field and double magnetic entropy change peaks: effect of ball-milling time on physical and critical behaviors

“…The magnetic refrigerators are expected to have a more condensed environmental impact than those based on traditional gas-compression refrigeration, parallel to their improved energy efficiency. This cooling method is based on the search for magnetic materials with important magnetocaloric effect (MCE) to be used as permanent magnets in the magnetic cooling technique, called also the 'green' refrigeration which presents an important field of research for scientists for its various advantages [1][2][3][4]. Nowadays, researchers concentrate principally on environmentally friendly magnetic materials for their various utilizations in heating, cooling, and 2.…”