Metal-insulator transition in colossal magnetoresistance materials

2000 ◽  
Vol 62 (5) ◽  
pp. 3010-3013 ◽  
Author(s):  
V. N. Smolyaninova ◽  
X. C. Xie ◽  
F. C. Zhang ◽  
M. Rajeswari ◽  
R. L. Greene ◽  
...  
Keyword(s):  
Colossal Magnetoresistance ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator

scholarly journals Effect of The Calcination Process On The Magnetotransport Properties in Co-Precipitation Derived La0.67Ca0.33MnO3 Ceramics

2021 ◽  
Author(s):  
Yule Li ◽  
Ping Yu ◽  
Xiaojin Wang ◽  
Fuxin Ling ◽  
Qingming Chen ◽  
...  
Keyword(s):  
Colossal Magnetoresistance ◽  
Sol Gel ◽  
Insulator Transition ◽  
Precipitation Method ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Calcination Process ◽  
Temperature Ranges ◽  
Lower Temperature ◽  
Co Precipitation

Abstract La0.67Ca0.33MnO3 (LCMO) attracts considerable attention as a quintessential example for colossal magnetoresistance (CMR), metal-insulator transition and related temperature coefficient of resistance (TCR) studies. Here, co-precipitation method was utilized to prepare the LCMO ceramics, whose magnetotransport properties as a function of calcination temperature (Tcal) and calcination time (tcal) were investigated. The magnetotransport properties of these LCMO ceramics were significantly enhanced compared with LCMO derived by sol-gel methods. The TCR of LCMO increased firstly and then decreased as the Tcal increased, whereas the metal-insulator transition temperature (TMIT) shifted towards to the lower temperature. Magnetoresistance (MR) increased as Tcal rose and reached 82.4 % at Tcal = 800 ℃. The mechanism of such magnetotransport properties with different temperature ranges was discussed. The optimal TCR of 32.3%·K-1 in LCMO was prepared with Tcal = 500 ℃ and tcal = 8 h, showing that co-precipitation method would facilitate the potential application of LCMO in infrared detecting and magnetoresistive switching.

DYNAMICS AND LOCAL STRUCTURE OF COLOSSAL MAGNETORESISTANCE MANGANITES

2000 ◽  
Vol 14 (25n27) ◽  
pp. 2725-2730 ◽  
Author(s):  
C. CASTELLANO ◽  
F. CORDERO ◽  
R. CANTELLI ◽  
C. MENEGHINI ◽  
S. MOBILIO ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Wide Temperature Range ◽  
Colossal Magnetoresistance ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Double Peak ◽  
Metal Insulator ◽  
Temperature Range ◽  
The Magnetic Field

We report Extended X-ray Absorption Fine Structure and anelastic spectroscopy measurements on hole doped manganese oxides La 1-x Ca x MnO 3 which present the colossal magnetoresistance effect. EXAFS measurements were realized both in the absence and presence of an applied magnetic field of 1.1 Tesla, in a wide temperature range (between 330 and 77 K) and at various dopings (x = 0.25 and x = 0.33). The magnetic field orders the magnetic moments so favouring the electron mobility and the reduction of Mn-O octahedra distortions. We observe the presence of four short and two long Mn-O distances (1.93 and 2.05Å respectively) above and also below the metal-insulator phase transition. The overall distortion decreases but does not completely disappear in the metallic phase suggesting the possible coexistence of metallic and insulating regions at low temperatures. The magnetic field reduces the lattice distortions showing evidence of a microscopic counterpart of the macroscopic colossal magnetoresistance. We also present preliminary anelastic relaxation spectra in a wide temperature range from 900 K to 1 K on a sample with x = 0.40, in order to study the structural phase transitions and the lattice dynamics. A double peak has been observed at the metal-insulator transition in the imaginary part of Young's modulus. This double peak indicates that the metal-insulator transition could be a more complex phenomenon than a simple second order phase transition. In particular the peak at lower temperatures can be connected with the possible presence of inhomogeneous phase structures. Another intense dissipation peak has been observed corresponding to the structural orthorhombic-trigonal transition around 750 K.

Fermi-surface reconstruction close to a pressure-induced metal-insulator transition

2004 ◽  
Vol 114 ◽  
pp. 277-281 ◽  
Author(s):  
J. Wosnitza ◽  
J. Hagel ◽  
O. Stockert ◽  
C. Pfleiderer ◽  
J. A. Schlueter ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Surface Reconstruction ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Fermi Surface Reconstruction
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