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Title: Magnetic, electrical, and optical properties of electron-doped Ca{sub 1-x}La{sub x}MnO{sub 3-{delta}}(x {<=} 0.12) single crystals

Abstract

The magnetic, electrical, and optical properties of Ca{sub 1-x}La{sub x}MnO{sub 3-{delta}}(x {<=} 0.12) manganite single crystals have been studied. The state with a spatially inhomogeneous electron distribution has been found. Interrelations between the electric and magnetic subsystems are analyzed. The obtained magnetic data show evidence for the formation of a G-type antiferromagnetic (G-AFM) phase with a spin-canted structure in the crystal with x = 0.05, for which the Curie and Neel temperatures are T{sub C} T{sub N}(G) = 115 K. On cooling from the paramagnetic state, the crystals with x 0.10 and 0.12 exhibit transitions from the paramagnetic to a C-type antiferromagnetic (C-AFM) phase in a part of the volume at T{sub N}(C) = 150 and 200 K, and from the paramagnetic to the G-type antiferromagnetic (G-AFM) phase in the remaining volume at T{sub N}(G) = 110 and 108 K, respectively. The onset of the C-type magnetic phase nucleation in crystals is observed at lower dopant (La) concentrations than in polycrystalline samples, which is explained by the deviation of single crystals from the stoichiometry with respect to oxygen. The magnetic phase transitions are manifested by anomalies in the electric resistance and magnetoresistance of doped crystals. An analysis of the electricalmore » and optical properties of the samples shows evidence of (i) the formation of a charge energy gap in the C-AFM phase with retained paramagnetic metallic regions and (ii) the presence of ferromagnetic 'metallic' droplets in the insulating G-AFM phase. The multiphase state of Ca{sub 1-x}La{sub x}MnO{sub 3-{delta}} manganite single crystals featuring the coexistence of two magnetic phases, the regions with orbital/charge ordering, and the FM 'metallic' droplets is related to a competition of exchange interactions by the superexchange and double exchange mechanisms.« less

Authors:
; ; ; ;  [1];  [2]
  1. Russian Academy of Science, Institute of Metal Physics, Ural Division (Russian Federation)
  2. Moscow Power Engineering Institute (Russian Federation)
Publication Date:
OSTI Identifier:
21067742
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 102; Journal Issue: 2; Other Information: DOI: 10.1134/S1063776106020051; Copyright (c) 2006 Nauka/Interperiodica; Article Copyright (c) 2006 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANTIFERROMAGNETISM; ATOMIC FORCE MICROSCOPY; CALCIUM COMPOUNDS; DOPED MATERIALS; ELECTRONS; EXCHANGE INTERACTIONS; LANTHANUM COMPOUNDS; MAGNETORESISTANCE; MANGANATES; MONOCRYSTALS; NEEL TEMPERATURE; NUCLEATION; OPTICAL PROPERTIES; PARAMAGNETISM; PHASE TRANSFORMATIONS; POLYCRYSTALS; SPIN; STOICHIOMETRY; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0065-0273 K

Citation Formats

Loshkareva, N. N., E-mail: loshkareva@imp.uran.ru, Korolev, A. V., Solin, N. I., Mostovshchikova, E. V., Naumov, S. V., and Balbashov, A. M. Magnetic, electrical, and optical properties of electron-doped Ca{sub 1-x}La{sub x}MnO{sub 3-{delta}}(x {<=} 0.12) single crystals. United States: N. p., 2006. Web. doi:10.1134/S1063776106020051.
Loshkareva, N. N., E-mail: loshkareva@imp.uran.ru, Korolev, A. V., Solin, N. I., Mostovshchikova, E. V., Naumov, S. V., & Balbashov, A. M. Magnetic, electrical, and optical properties of electron-doped Ca{sub 1-x}La{sub x}MnO{sub 3-{delta}}(x {<=} 0.12) single crystals. United States. doi:10.1134/S1063776106020051.
Loshkareva, N. N., E-mail: loshkareva@imp.uran.ru, Korolev, A. V., Solin, N. I., Mostovshchikova, E. V., Naumov, S. V., and Balbashov, A. M. Wed . "Magnetic, electrical, and optical properties of electron-doped Ca{sub 1-x}La{sub x}MnO{sub 3-{delta}}(x {<=} 0.12) single crystals". United States. doi:10.1134/S1063776106020051.
@article{osti_21067742,
title = {Magnetic, electrical, and optical properties of electron-doped Ca{sub 1-x}La{sub x}MnO{sub 3-{delta}}(x {<=} 0.12) single crystals},
author = {Loshkareva, N. N., E-mail: loshkareva@imp.uran.ru and Korolev, A. V. and Solin, N. I. and Mostovshchikova, E. V. and Naumov, S. V. and Balbashov, A. M.},
abstractNote = {The magnetic, electrical, and optical properties of Ca{sub 1-x}La{sub x}MnO{sub 3-{delta}}(x {<=} 0.12) manganite single crystals have been studied. The state with a spatially inhomogeneous electron distribution has been found. Interrelations between the electric and magnetic subsystems are analyzed. The obtained magnetic data show evidence for the formation of a G-type antiferromagnetic (G-AFM) phase with a spin-canted structure in the crystal with x = 0.05, for which the Curie and Neel temperatures are T{sub C} T{sub N}(G) = 115 K. On cooling from the paramagnetic state, the crystals with x 0.10 and 0.12 exhibit transitions from the paramagnetic to a C-type antiferromagnetic (C-AFM) phase in a part of the volume at T{sub N}(C) = 150 and 200 K, and from the paramagnetic to the G-type antiferromagnetic (G-AFM) phase in the remaining volume at T{sub N}(G) = 110 and 108 K, respectively. The onset of the C-type magnetic phase nucleation in crystals is observed at lower dopant (La) concentrations than in polycrystalline samples, which is explained by the deviation of single crystals from the stoichiometry with respect to oxygen. The magnetic phase transitions are manifested by anomalies in the electric resistance and magnetoresistance of doped crystals. An analysis of the electrical and optical properties of the samples shows evidence of (i) the formation of a charge energy gap in the C-AFM phase with retained paramagnetic metallic regions and (ii) the presence of ferromagnetic 'metallic' droplets in the insulating G-AFM phase. The multiphase state of Ca{sub 1-x}La{sub x}MnO{sub 3-{delta}} manganite single crystals featuring the coexistence of two magnetic phases, the regions with orbital/charge ordering, and the FM 'metallic' droplets is related to a competition of exchange interactions by the superexchange and double exchange mechanisms.},
doi = {10.1134/S1063776106020051},
journal = {Journal of Experimental and Theoretical Physics},
number = 2,
volume = 102,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}
  • The magnetic, electrical, and optical properties of Ca{sub 1-x}Ce{sub x}MnO{sub 3} (x{<=}0.12) manganite single crystals are investigated with the aim of revealing the specific features of the multiphase electronic and magnetic state as a function of the cerium concentration and the atmosphere used for growing single crystals. It is found that the concentration dependence of the low-temperature magnetization M(x) of the single crystals is shifted toward the high-concentration range as compared to the corresponding dependence of the polycrystals, which is explained by the predominant cation deficiency. The electrical resistivity and the reflection spectra of the single crystals in the infraredmore » spectral range indicate that charge carriers exhibit a band nature at temperatures close to room temperature. The temperature dependence of the electrical resistivity of the single crystal with x = 0.08, which has the maximum magnetization in the studied series of Ca{sub 1-x}Ce{sub x}MnO{sub 3} compounds, unlike polycrystals, exhibits a metallic behavior over the entire temperature range. The G-type antiferromagnetic phase with the Neel and Curie temperatures T{sub N}(G) = T{sub C} = 100 K is characterized by maxima of the electrical resistivity {rho} and the magnetoresistance {delta}{rho}/{rho} = vertical bar ({rho}{sub 0} - {rho}{sub H})/{rho}{sub 0} vertical bar = 38% in the magnetic field H = 90 kOe. The magnetoresistance {delta}{rho}/{rho} of the single crystals at cerium concentrations x = 0.10 and 0.12 with variations in temperature exhibit three specific features: near the temperature of charge ordering T{sub co}, near the temperature of the magnetic phase transition to the C-type antiferromagnetic phase T{sub N}(C), and near the temperature of the phase transition to the magnetic charge-ordered phase T{sub N}(MCO). An anomalous temperature dependence of the magnetization is revealed for a single crystal with x = 0.10 grown in oxygen at a pressure of 5 atm, which is explained by the presence of regions with hole conductivity due to cation deficiency. The inhomogeneous electronic and magnetic state is associated with the interrelation of the charge, orbital, and spin orderings.« less
  • We report the electrical-transport, magnetoresistance and magnetic properties of the hole doped La{sub 0.7}Ca{sub 0.3}MnO{sub 3} (LCMO) and La{sub 0.7}Ca{sub 0.24}Sr{sub 0.06}MnO{sub 3} (LCSMO) single crystals. It was prepared using floating zone technique. The resistivity data shows the metal to insulator transition (T{sub MI}) occurs at 211 K along c-axis and T{sub MI} = 185 K the ab-plane for LCMO and T{sub MI} = 290 K along the c-axis and T{sub MI} = 280 K along the ab-plane for LCSMO single crystals. It is observed that the T{sub MI} is higher along the c-axis as compared to that in the ab-plane, consequently signifying moremore » favorable hoping of electrons is along the c-axis. The ac-susceptibility measurement shows that this material exhibits ferromagnetic to paramagnetic transition temperature (TC) at 206 K for LCMO and T{sub C} = 277 K for LCSMO single crystals. For magnetic memory device application point of view, the sample shows the maximum MR of 98% for LCMO and 80% for LCSMO single crystals at 8T applied magnetic field. Doping small amount of Sr (0.06%) reveals that the electronic and magnetic phase transition in CMR single crystal increases substantially and useful for device application. This is first time such type of comparative study in these manganite single crystals.« less
  • X-ray, neutron powder diffraction (NPD), and magnetic measurements were performed in order to investigate the effect of Pr substitution for La on crystallographic structure, on character of magnetic ordering, and on transition temperature in La{sub 1-x}Pr{sub x}MnO{sub 3+{delta}} manganites series (0{<=}x{<=}1.0). Strong dependence of structural and magnetic properties on average A-site ionic radius was found. The magnetic phase diagram, characterizing Pr concentration dependence of the phase transition temperature, was constructed, based on magnetic and on NPD results. In the compounds with x<0.7, the ferromagneticlike behavior with ferromagnetic moment aligned along the b axis was observed in the temperature interval belowmore » the Curie temperature, T{sub C}, varying in the range of 113-153 K, down to Mn ions canted spin arrangement transition temperature, T{sub CANT}, varying in the range of 73-115 K. It was found that T{sub C} changes nonmonotonously with Pr content, it decreases rapidly for x<0.3 and for x>0.6, while is practically independent on x for 0.3<x<0.6. The Mn magnetic moments increase from 3.2 for x=0 to 3.6 for x=0.3 before decreasing to 1.7 {mu}{sub B}/Mn for x=1.0 and form a canting structure with canting angle decreasing from 32 deg. for x=0 to 16 deg. for x=0.3 and then increasing to 70 deg. for x=1.0. The NPD and x-ray diffraction data indicate that Pr doping in LaMnO{sub 3} is accompanied by changes of both the lattice parameters and crystal structure. The compound with x=0 was shown to have a rhombohedral crystal structure, while the samples with 0.1{<=}x{<=}0.6 have orthorhombic symmetry with a small Jahn-Teller distortion (or pseudocubic) which continuously transforms towards highly distorted orthorhombic structure for x>0.6. From ac magnetic susceptibility, studied under hydrostatic pressure up to 1.5 GPa, it was found that T{sub C} and T{sub CANT} change linearly with an applied pressure. The results are interpreted taking into account the competition of ferromagnetic double-exchange and antiferromagnetic superexchange interactions. This competition leads to a low temperature disordered system with spin canted features as a result of a decrease of the average A-site cation radius followed by decrease of Mn-O bond lengths, Mn-O-Mn bond angles, and the static Jahn-Teller distortion of the MnO{sub 6} octahedra.« less
  • The magnetic properties of electron-doped perovskite manganites, (Gd{sub x}Ca{sub y}Sr{sub 1-x-y})MnO{sub 3} (x=0.08 and 0.05, 0.1{<=}y<1), were investigated as a function of the average ionic radius of the A-site cations (i.e., Gd, Ca and Sr), <r{sub A}>using polycrystalline samples. For the samples with x=0.08, as y increased from 0, the low temperature phase changed from an antiferromagnetic insulator (AFI) to a ferromagnetic metal (FM) at y{approx}0.35 which corresponds to <r{sub A}>=1.25 A. The magnitude of the Neel temperature was found to correlate with the bandwidth of the Mn-3d band. On the other hand, for the samples with y>0.5, a smallmore » saturation magnetization suggested the coexistence of the FM and AFI phase; in other words, magnetic phase separation occurred below the Curie temperature ({approx}120 K). A scaling analysis of the resistivity of (Gd{sub 0.08}Ca{sub y}Sr{sub 0.92-y})MnO{sub 3} indicated that a percolation transition between FM clusters was induced by the decrease in <r{sub A}>.« less
  • We have investigated electrical-transport, magneto-transport, magnetic and thermal properties of the hole doped La{sub 0.7}Ca{sub 0.24}Sr{sub 0.06}MnO{sub 3} (LCSMO) and La{sub 0.88}Ca{sub 0.12}MnO{sub 3} (LCMO) single crystals, prepared using floating zone technique. The crystallographic direction dependence of metal to insulator transition (T{sub P}) occurs at 290 K along c-axis and T{sub P} = 280 K along ab-plane for LCSMO single crystal, while no electronic transition was observed over the whole temperature range under the magnetic field at 8 T for LCMO single crystal. Resistivity study shows that the T{sub P} is higher along the c-axis as compared to that in the ab-plane,more » so signifying more favorable hoping of electrons is along the c-axis in LCSMO. The ac-susceptibility study confirms that these crystals, revealing ferromagnetic to paramagnetic transition temperature (T{sub C}) at 277 K for LCSMO and T{sub C} = 118 K for LCMO single crystals, which is close to the sharp peak around T{sub C} in heat capacity data. For magneto-electric device application point of view, these crystals show the maximum MR of 80% and 65% for LCSMO and LCMO single crystals at 8 T applied magnetic field respectively.« less