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  • 1
    Electronic Resource
    Electronic Resource
    Ultrasonic study on charge ordering, magnetic, and structural changes in La0.25Ca0.75Mn0.93Cr0.07O3 (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1173-1175 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The longitudinal and transverse ultrasonic velocities and attenuations, the transport and magnetic properties, as well as the structural changes of polycrystalline La0.25Ca0.75Mn0.93Cr0.07O3 have been studied systematically. A velocity minimum and an attenuation peak for both longitudinal and transverse waves occur around the temperature Tco of charge ordering transition accompanied by the structural change from a cubic to a tetragonal phase. Near temperature TN (where the c-axis length shows a maximum), the sharp decrease of velocities for both waves and the appearance of a longitudinal attenuation peak are attributed to the antiferromagnetic transition together with the anomalous change in c-axis length of the tetragonal phase. The simultaneous occurrence of the ultrasonic, lattice, charge ordering, magnetic, and transport anomalous characteristics indicates the strong electron–phonon and spin–phonon interactions in the system. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125974
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  • 2
    Electronic Resource
    Electronic Resource
    Transport properties of La 1 - x Ca x MnO 3 ( 0.5 ? x 〈 1) (2002)
    Springer
    The European physical journal 26 (2002), S. 467-471 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 72.20.Ht High-field and nonlinear effects – 72.60.+g Mixed conductivity and conductivity transitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The transport properties of the La1-xCaxMnO3 ( 0.5 ? x 〈 1) system in magnetic fields up to 14 T were studied. We found that the relationship between the charge ordering temperature T CO and Mn4+ content n Mn4 + obeys the formula T CO / T max = 1 - a ( n Mn4 + - n 0 ) 2 , here n0 and a are constants and T max is the maximum of T CO . For x = 0.65, T CO arrives at the maximum value of 249.5 K in zero magnetic field, while the charge ordered (CO) state is most stable around x = 0.75. For x = 0.5 when H 〈 6 T the resistivity displays Mott's variable-range hopping (VRH) behavior, when 6 〈 H 〈 12 T it is suggested that two kinds of conduction mechanism, i.e., VRH and magnetic polarons, coexist in the material, and when H 〉 12 T the resistivity shows metallic-like behavior and the transport mechanism is attributed to coexistence of magnetic polarons and free carriers. For x = 0.95, the conduction mechanism accords with the coexistence of VRH and magnetic polarons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e20020115
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  • 3
    Electronic Resource
    Electronic Resource
    Insulator-metal transition shift related to magnetic polarons in La 0.67- xY xCa 0.33MnO 3 (2003)
    Springer
    The European physical journal 32 (2003), S. 5-11 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.30.Vn Colossal magnetoresistance – 71.30.+h Metal-insulator transitions and other electronic transitions – 76.30.-v Electron paramagnetic resonance and relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The magnetic transport properties have been measured for La0.67-xYxCa0.33MnO3 ( 0 ⩽ x ⩽ 0.14) system. It was found that the transition temperature T p almost linearly moves to higher temperature as H increases. Electron spin resonance confirms that above T p , there exist ferromagnetic clusters. From the magnetic polaron point of view, the shift of T p vs. H was understood, and it was estimated that the size of the magnetic polaron is of 9.7 ∼ 15.4 Å which is consistent with the magnetic correlation length revealed by the small-angle neutron-scattering technique. The transport properties at temperatures higher than T p conform to the variable-range hopping mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00068-8
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