Orbital ordering in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">LaMnO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mo>:</mml:mo></mml:math>Electron-electron and electron-lattice interactions

We investigate antiferro quadrupole orders in a diamond lattice under magnetic fields by Monte Carlo simulations for two types of classical effective models. One is an XY model with Z3 anisotropy, and the other is a two-component φ 4 model with a third-order anisotropy. We confirm that the universality class of the zero-field transition is that for the three-dimensional XY model. Magnetic field corresponds to a Z3 field in the effective model, and under this field, we find that collinear and canted antiferro-quadrupole orders compete. Each phase is characterized by symmetry breaking in the sector of (sublattice Z2)⊗(reflection Z2 for the order parameter). When Z3 anisotropy and magnetic field vary, it turns out that this system is a good playground for various multicritical points; bicritical and tetracritical points emerge in a finite field. Another important finding is about the scaling of parasitic ferro quadrupole order at the zero-field critical point. This is the secondary order parameter induced by the primary antiferro order, and its critical exponent β ′ =0.815 clearly differs from the expected value that is twice the value for the primary order parameter. The corresponding correlation length exponent is also different, ν ′ =0.597(12). We also discuss relation of the present effective quadrupole models with the 3-state Potts model as well as implication to undertanding of orbital orders in Pr-based 1-2-20 compounds.

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“…Indeed, these anisotropic interactions are known to be very important in a context of the orbital orders in LaMnO 3 . 40,41) …”

Section: Comparison To the Antiferro 3-state Potts Modelmentioning

confidence: 99%

Classical Monte Carlo Study for Antiferro Quadrupole Orders in a Diamond Lattice

Hattori

Tsunetsugu

2016

J. Phys. Soc. Jpn.

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“…The crystal structure contains tilted and rotated MnO 6 octahedra along with cooperative JT instabilities characterized by two short (s = 1.903Å), two long (l = 2.184Å), and two medium (m = 1.957Å) Mn-O bond distances [27]. These distortions lift the degeneracy of the singly occupied e g orbital and stabilize the system into an orbital-ordered state [28,29]. Hole-doping or raising the temperature produce a pseudo-cubic structure with FM half-metallic character [24,30,31] and small volume decrease of 2-4%.…”

Section: Introductionmentioning

confidence: 99%

Uniaxial pressure-induced half-metallic ferromagnetic phase transition inLaMnO3

2016

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We use first-principles theory to predict that the application of uniaxial compressive strain leads to a transition from an antiferromagnetic insulator to a ferromagnetic half-metal phase in LaMnO3. We identify the Q2 Jahn-Teller mode as the primary mechanism that drives the transition, indicating that this mode can be used to tune the lattice, charge, and spin coupling. Applying ≃ 6 GPa of uniaxial pressure along the [010] direction activates the transition to a half-metallic pseudo-cubic state. The half-metallicity opens the possibility of producing colossal magnetoresistance in the stoichiometric LaMnO3 compound at significantly lower pressure compared to recently observed investigations using hydrostatic pressure.

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“…Different points of view have been reported regarding the relative importance of the inter-and intra-orbital Hubbard interactions and the JT interaction in the manganites [23,24]. Although the electron-electron (ee) interactions are large in these systems, it has been suggested that the parent insulator can not be considered as a canonical Mott insulator [25].…”

Section: Introductionmentioning

confidence: 99%

Effect of disorder in an orbitally ordered Jahn-Teller insulator

2007

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We study a two dimensional, two-band double-exchange model for eg electrons coupled to JahnTeller distortions in the presence of quenched disorder using a recently developed Monte-Carlo technique. In the absence of disorder the half-filled system at low temperatures is an orbitally ordered ferromagnetic insulator with a staggered pattern of Jahn-Teller distortions. We examine the finite temperature transition to the orbitally disordered phase and uncover a qualitative difference between the intermediate and strongly coupled systems, including a thermally driven insulator to metal crossover in the former case. Long range orbital order is suppressed in the presence of disorder and the system displays a tendency towards metastable states consisting of orbitally disordered stripe-like structures enclosing orbitally ordered domains.

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Orbital ordering inLaMnO3:Electron-electron and electron-lattice interactions

Cited by 72 publications

References 48 publications

Classical Monte Carlo Study for Antiferro Quadrupole Orders in a Diamond Lattice

Classical Monte Carlo Study for Antiferro Quadrupole Orders in a Diamond Lattice

Uniaxial pressure-induced half-metallic ferromagnetic phase transition inLaMnO3

Effect of disorder in an orbitally ordered Jahn-Teller insulator

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