Spiral State and Giant Magnetoresistance in Perovskite Mn Oxides

Inoue, Jun–ichiro; Maekawa, Sadamichi

doi:10.1103/physrevlett.74.3407

Cited by 193 publications

(121 citation statements)

References 26 publications

Supporting

Mentioning

113

Contrasting

Unclassified

Order By: Relevance

“…Inoue et al [14] also obtained similar expression in the DE limit and suggested that a spiral state may be more stable than the canted state in La 1−x R x MnO 3 , but they did not consider the effect of the Coulomb interaction on the ground state and the possibility of phase separation. Later we will show that the Coulomb correlation can not be neglected.…”

Section: Diagonalization In Momentum Spacementioning

confidence: 70%

Ground state of the double-exchange model

1997

View full text Add to dashboard Cite

We investigate the electronic correlation effect on the ground-state properties of the double exchange model for manganites by using a semiclassical approach and the slave-boson technique. It is shown that magnetic field has a similar effect on the canted angle between manganese spins as doping concentration does, and the canted angle exhibits weak dependence on the Coulomb interaction. The possibility of phase separation in the present model is also discussed. In the slave-boson saddle-point approximation in the ferromagnetic metallic regime, the dependence of the magnetization and the Curie temperature on the doping concentration exhibits maxima near 1/3 doping. These results agree with experimental data and suggest that the electronic correlation plays an important role for understanding the ground-state properties of manganites.

show abstract

Section: Diagonalization In Momentum Spacementioning

confidence: 70%

Ground state of the double-exchange model

1997

View full text Add to dashboard Cite

show abstract

“…One possibility is so-called J terms, i.e., L J in Eq. (6). It is noted that the transfer matrix t ij = (t γγ ′ ij ) does not commute with any of the Pauli matrices σ α .…”

mentioning

confidence: 99%

“…The valency of Mn ion is Mn 3+ for x = 0, whose electron configuration is (t 2g ) 3 (e g ) 1 , and all the spins are aligned ferromagnetically due to the strong Hund coupling. Because of the strong on-site repulsion, the double occupancy of e g orbitals is forbidden [5,6], and the system is a Mott insulator. When one La is replaced by Sr, one hole is introduced to Mn and Mn 3+ turns into Mn 4+ .…”

mentioning

confidence: 99%

Orbital liquid in perovskite transition-metal oxides

1997

View full text Add to dashboard Cite

We study the effects of the degeneracy of the eg orbitals as well as the double exchange interaction with t2g spins in perovskite transition-metal oxides. In addition to the spin field Si, the isospin field Ti is introduced to describe the orbital degrees of freedom. The isospin is the quantum dynamical variable, and is represented by the boson with a constraint. The dispersion of this boson is flat along (π/a, π/a, kz) (a: lattice constant) and the other two equivalent directions. This enables the orbital disordered phase down to low temperatures. We interpret some of the anomalous experiments, i.e., optical absorption and d.c. resistivity, in the low temperature ferromagnetic phase of La1−xSrxMnO3 with x > 0.2 in terms of this orbital liquid picture. 71.27.+a, 71.30.+h, 75.30.Et The colossal negative magneto-resistance observed in transition-metal oxides with perovskite structure, e.g., the double exchange system La 1−x Sr x MnO 3 , has revived the interest in these systems [1][2][3][4]. The valency of Mn ion is Mn 3+ for x = 0, whose electron configuration is (t 2g ) 3 (e g ) 1 , and all the spins are aligned ferromagnetically due to the strong Hund coupling. Because of the strong on-site repulsion, the double occupancy of e g orbitals is forbidden [5,6], and the system is a Mott insulator. When one La is replaced by Sr, one hole is introduced to Mn and Mn 3+ turns into Mn 4+ . These doped holes, which contribute to the conduction, can not be described in terms of the one-body theory. For a single band case, which is relevant to high-Tc cuprates, extensive studies have been focused on these doped holes to a Mott insulator. One of the promising approaches is resonating valence bond (RVB) theory [7,8], where the spin and charge are separated. In the orbital-degenerate case, this idea can be generalized also to the orbital degrees of freedom as shown below [9].Experimentally the orbital ordering has been established in the low hole-concentration region, i.e., x ∼ 0.0 [10], where the system is insulating with the A-type antiferromagnetic long range ordering (AFLRO) [11]. As x increases the system becomes more and more conductive, and finally shows the metallic conduction below the ferromagnetic transition temperature T c . In this metallic state (x > 0.2), there are several anomalous features.(1) The optical conductivity shows a narrow coherent peak up to around 0.02eV followed by a broader "Drude like" band up to around 1eV [12]. The integrated oscillator strength for this two-component Drude absorption changes down to the very low temperature where the ferromagnetic moment already saturates, which suggests that other degrees of freedom still remain active.(2) The photoemission spectra shows only a small discontinuity at the Fermi energy E F followed by a gap like behavior [13][14][15]. On the other hand, the specific heat is not enhanced with γ ∼ 5mJ/K 2 mol [15]. (3) The anisotropy of the conduction and the spin excitation, which is expected with the orbital ordering, is not observed even at low temperature...

show abstract

“…The phase diagrams of doped manganites, especially for magnetic and orbital ordering, have been investigated. [23][24][25][26][27][28] Recent overviews for doped manganites are seen in Ref. 29,30 .…”

Section: Introductionmentioning

confidence: 99%

Phase separation and charge ordering in doped manganite perovskites: Projection perturbation and mean-field approaches

Shen

Wang

2000

Phys. Rev. B

View full text Add to dashboard Cite

A unified theory is developed to explain various types of electronic collective behaviors in doped manganites R1−xXxMnO3 (R = La, Pr,Nd etc. and X = Ca, Sr, Ba etc.). Starting from a realistic electronic model, we derive an effective Hamiltonianis by ultilizing the projection perturbation techniques and develop a spin-charge-orbital coherent state theory, in which the Jahn-Teller effect and the orbital degeneracy of eg electrons in Mn ions are taken into account. Physically, the experimentally observed charge ordering state and electronic phase separation are two macroscopic quantum phenomena with opposite physical mechanisms, and their physical origins are elucidated in this theory. Interplay of the Jahn-Teller effect, the lattice distortion as well as the double exchange mechanism leads to different magnetic structures and to different charge ordering patterns and phase separation.

show abstract

Spiral State and Giant Magnetoresistance in Perovskite Mn Oxides

Cited by 193 publications

References 26 publications

Ground state of the double-exchange model

Ground state of the double-exchange model

Orbital liquid in perovskite transition-metal oxides

Phase separation and charge ordering in doped manganite perovskites: Projection perturbation and mean-field approaches

Contact Info

Product

Resources

About