scholarly journals Optical conductivity of colossal-magnetoresistance compounds: Role of orbital degeneracy in the ferromagnetic phase

1999 ◽  
Vol 59 (9) ◽  
pp. 6217-6228 ◽  
Author(s):  
Peter Horsch ◽  
Janez Jaklič ◽  
Frank Mack
Keyword(s):  
Optical Conductivity ◽  
Colossal Magnetoresistance ◽  
Ferromagnetic Phase ◽  
Orbital Degeneracy

scholarly journals ORBITAL EFFECTS IN MANGANITES

2001 ◽  
Vol 15 (19n20) ◽  
pp. 2665-2681 ◽  
Author(s):  
D. I. KHOMSKII
Keyword(s):  
Phase Diagram ◽  
Colossal Magnetoresistance ◽  
Degrees Of Freedom ◽  
Short Review ◽  
Orbital Ordering ◽  
Orbital Degeneracy ◽  
Structural Distortions ◽  
Jahn Teller ◽  
Different Parts

In this paper I give a short review of some properties of the colossal magnetoresistance manganites, connected with the orbital degrees of freedom. Ions Mn 3+, present in most of these compounds, have double orbital degeneracy and are strong Jahn–Teller ions, causing structural distortions and orbital ordering. Mechanisms leading to such ordering are shortly discussed, and the role of orbital degrees of freedom in different parts of the phase diagram of manganites is described. Special attention is paid to the properties of low-doped systems (doping 0.1≤x≤0.25), to overdoped systems (x>0.5), and to the possibility of a novel type of orbital ordering in optimally doped ferromagnetic metallic manganites.

scholarly journals Theory of high-energy optical conductivity and the role of oxygens in manganites

2011 ◽  
Vol 84 (7) ◽  
Author(s):  
Muhammad Aziz Majidi ◽  
Haibin Su ◽  
Yuan Ping Feng ◽  
Michael Rübhausen ◽  
Andrivo Rusydi
Keyword(s):  
Optical Conductivity ◽  
High Energy

scholarly journals Strong anisotropic optical conductivity in two-dimensional puckered structures: The role of the Rashba effect

2017 ◽  
Vol 96 (7) ◽  
Author(s):  
S. Saberi-Pouya ◽  
T. Vazifehshenas ◽  
T. Salavati-fard ◽  
M. Farmanbar ◽  
F. M. Peeters
Keyword(s):  
Optical Conductivity ◽  
Two Dimensional ◽  
Rashba Effect

PHONON-ENHANCED KONDO LATTICE MODEL IN COLOSSAL MAGNETORESISTIVE MANGANITES

2006 ◽  
Vol 20 (01) ◽  
pp. 25-29
Author(s):  
JE HUAN KOO ◽  
GUANGSUP CHO
Keyword(s):  
Lattice Model ◽  
Colossal Magnetoresistance ◽  
Manganese Oxides ◽  
Kondo Lattice ◽  
Colossal Magnetoresistive ◽  
Hole Conduction ◽  
Kondo Lattice Model ◽  
Jahn Teller ◽  
Peierls Transition

We investigate theoretically manganese oxides where the colossal magnetoresistance (CMR) is observed. Recent studies show that, if there are both an electron and a hole in the eg-band of Mn , the Jahn–Teller distortions split the band into a conduction band [Formula: see text] and a localized band [Formula: see text]. We find a Kondo lattice model with hole conduction in manganese oxides when the electron in the localized eg-band [Formula: see text] plays the role of the Kondo impurity. The Curie temperature (Tc) and the resistivity are calculated. We also calculate the antiferromagnetic temperature by a spin-Peierls transition.

Role of external and internal perturbations on the ferromagnetic phase transition inSm0.52Sr0.48MnO3

2009 ◽  
Vol 79 (14) ◽  
Author(s):  
P. Sarkar ◽  
P. Mandal ◽  
K. Mydeen ◽  
A. K. Bera ◽  
S. M. Yusuf ◽  
...  
Keyword(s):  
Phase Transition ◽  
Ferromagnetic Phase ◽  
Ferromagnetic Phase Transition

scholarly journals Origin of colossal magnetoresistance in LaMnO3 manganite

2015 ◽  
Vol 112 (35) ◽  
pp. 10869-10872 ◽  
Author(s):  
Maria Baldini ◽  
Takaki Muramatsu ◽  
Mohammad Sherafati ◽  
Ho-kwang Mao ◽  
Lorenzo Malavasi ◽  
...  
Keyword(s):  
Phase Separation ◽  
Percolation Threshold ◽  
Memory Effect ◽  
Percolation Theory ◽  
Colossal Magnetoresistance ◽  
Magnetic Clusters ◽  
Model Hamiltonian ◽  
Large Memory ◽  
Crucial Ingredient

Phase separation is a crucial ingredient of the physics of manganites; however, the role of mixed phases in the development of the colossal magnetoresistance (CMR) phenomenon still needs to be clarified. We report the realization of CMR in a single-valent LaMnO3 manganite. We found that the insulator-to-metal transition at 32 GPa is well described using the percolation theory. Pressure induces phase separation, and the CMR takes place at the percolation threshold. A large memory effect is observed together with the CMR, suggesting the presence of magnetic clusters. The phase separation scenario is well reproduced, solving a model Hamiltonian. Our results demonstrate in a clean way that phase separation is at the origin of CMR in LaMnO3.

Conductivity and Isotope Effect in the Colossal Magnetoresistance

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3397-3405 ◽  
Author(s):  
Y. M. Malozovsky ◽  
J. D. Fan ◽  
D. Bagayoko
Keyword(s):  
Curie Temperature ◽  
Isotope Effect ◽  
Colossal Magnetoresistance ◽  
Manganese Oxides ◽  
Spin Diffusion ◽  
Magnetic Moments ◽  
Ferromagnetic Phase ◽  
Temperature Dependence Of Conductivity ◽  
Ferromagnetic Phase Transition ◽  
Localized Electrons

The diffusion of nearly localized electrons is considered in the presence of the spin-dependent and multiple scattering on the randomly oriented and/or distributed magnetic moments of scatterers. The spin diffusion coefficient in the case of the exchange interaction between the diffusive but nearly localized electrons is evaluated. It is shown that the electron localization leads to the vanishing of the spin diffusion and hence the ferromagnetic phase transition. The isotope effect in the Curie temperature in the case of the electron–phonon inelastic relaxation is obtained, as experimentally observed in the manganese oxides by Zhao and co-workers.11 The strong spin-polaron effect caused by the interaction of the diffusive electrons with the diffusive paramagnons significantly reduces conductivity near the Curie temperature. The temperature dependence of conductivity in the absence and presence of an external magnetic field is discussed as well.

Chemical disorder effects in transport and magnetic properties of perovskite manganite

2005 ◽  
Vol 20 (4) ◽  
pp. 813-817
Author(s):  
Subhayan Biswas ◽  
Sandip Chatterjee ◽  
P. Chatterjee ◽  
A.K. Nigam ◽  
S.K. De
Keyword(s):  
Magnetic Properties ◽  
Colossal Magnetoresistance ◽  
Lattice Mismatch ◽  
Perovskite Manganite ◽  
The Novel ◽  
Ionic Radii ◽  
Three Samples ◽  
Moderate Magnetic Field ◽  
A Site

The dependence of the novel properties observed in colossal magnetoresistance (CMR) materials, other than average ionic radii 〈rA〉 and Mn valence ratio (Mn3+/Mn4+), was investigated through examination of the transport and magnetic properties of Pr0.65(Ca0.7Sr0.3)0.35MnO3, La0.123Pr0.527(Ca0.8Sr0.2)0.35MnO3, and Pr0.65(Ca0.866Ba0.134)0.35MnO3. The average ionic radii 〈rA〉 and valence ratio of all three samples have been kept equal. The results of this investigation indicate a more intense role of the nature of individual A-site cation and the lattice mismatch. A remarkably large magnetoresistance of the order of 108 at moderate magnetic field has been observed for Ba-doped sample.

scholarly journals p-Wave Pairing and Colossal Magnetoresistance in Manganese Oxides

1998 ◽  
Vol 12 (13) ◽  
pp. 507-518 ◽  
Author(s):  
Yong-Jihn Kim
Keyword(s):  
Colossal Magnetoresistance ◽  
Manganese Oxides ◽  
P Wave ◽  
Ferromagnetic Phase ◽  
Sharp Drop ◽  
Wave Pairing ◽  
Magnetic Inhomogeneities ◽  
Gap Opening ◽  
Superconducting Fluctuations ◽  
Room Temperature Superconductivity

We point out that the existing experimental data of most manganese oxides show the frustratedp-wave superconducting condensation in the ferromagnetic phase in the sense that the superconducting coherence is not long enough to cover the whole system. The superconducting state is similar to the A1 state in superfluid He-3. The sharp drop of resistivity, the steep jump of specific heat, and the gap opening in tunneling are well understood in terms of the p-wave pairing. In addition, colossal magnetoresistance (CMR) is naturally explained by the superconducting fluctuations with increasing magnetic fields. The finite resistivity may be due to some magnetic inhomogeneities. This study leads to the possibility of room temperature superconductivity.

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