Behavior of the atomic and magnetic structure of La0.35Pr0.35Ca0.30MnO3 at a metal-insulator phase transition

Structural and magnetic properties of the colossal magnetoresistance perovskiteLa0.85Ca0.15MnOLobanov1, Балагуров2, Pomjakushin3 et al. 2000Phys. Rev. BSelf Cite503370View full textAdd to dashboardCite

“…A very small but clearly seen cell volume discontinuity occurs at a temperature just below T C . The volume jump in this compound is about 0.035% which is nearly four 20 but still more than 100 times larger than the typical value for conventional FM crystals.…”

Effect of oxygen isotope substitution on the magnetic structure of(La0.25Pr0.75)Балагуров1, Pomjakushin2, Sheptyakov3 et al. 1999Phys. Rev. BSelf Cite565340View full textAdd to dashboardCite

“…In our previous neutron diffraction study of (La 0.5 Pr 0.5 ) 0.7 Ca 0.3 MnO 3 with natural oxygen isotope content, 15 it was shown that the phase transition to the metallic state occurs simultaneously with FM ordering, and is accompanied by a jump in the unit cell volume and ''melting'' of the orbital ordering of Mn-O bonds. In the present paper we report experimental data obtained for (La 0.25 Pr 0.75 ) 0.7 Ca 0.3 MnO 3 by the neutron diffraction technique.…”

Anomalous temperature behavior of the resistivity in lightly doped manganites around a metal-insulator phase transition

“…The observed phenomenon is thought to arise from competition between substitution induced strengthening of potential barriers (which hamper the charge hopping between neighboring M n sites) and weakening of carrier's kinetic energy. The data are well fitted assuming a nonthermal tunneling conductivity theory with randomly distributed hopping sites.PACS numbers: 71.30.+h, 75.50.Cc, 71.27.a To clarify the underlying microscopic transport mechanisms in exhibiting colossal magnetoresistance manganites, numerous studies (both experimental and theoretical) have been undertaken during the past few years [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] which revealed a rather intricate correlation of structural, magnetic and charging properties in these materials based on a crucial role of the M n 3+ −O−M n 4+ network. In addition to the so-called double-exchange (DE) mechanism (allowing conducting electrons to hop from the singly occupied e 2g orbitals of M n 3+ ions to empty e 2g orbitals of neighboring M n 4+ ions), these studies emphasized the important role of the Jahn-Teller (JT) mechanism associated with the distortions of the network's bond angle and length and leading to polaron formation and electron localization in the paramagnetic insulating region.…”

“…In turn, the onset of ferromagnetism below Curie point increases the effective bandwidth with simultaneous dissolving of spin polarons into band electrons and rendering material more metallic. To modify this network, the substitution effects on the properties of the most popular La 0.7 Ca 0.3 M nO 3 manganites have been studied including the isotopic substitution of oxygen ("giant" isotope effect [8,9]), rare-earth (RE) [10][11][12][13][14] and transition element (TE) [15][16][17] doping at the M n site. In particular, an unusually sharp decrease of resistivity ρ(T ) in La 0.7 Ca 0.3 M n 0.96 Cu 0.04 O 3 due to just 4% Cu doping has been reported [17] and attributed to the Cu induced weakening of the kinetic carrier's energy E 0 (x).…”