Superexchange interaction in insulating manganites<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>R</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>A</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">MnO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn><

Gontchar, L. E.; Никифоров, А. Е.

doi:10.1103/physrevb.66.014437

Cited by 34 publications

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“…The remarkable change with decreasing φ is seen in the SE interaction between Mn(1) and Mn(3) along the b-axis; it turns to a strong AF interaction from a weak FM one [see J 2 in the inset of Fig. 3(a)] as well as weakening of the NN FM one (J 1 ) [17,18].…”

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Distorted perovskite witheg1configuration as a frustrated spin system

et al. 2003

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The evolution of spin-and orbital-ordered states has been investigated for a series of insulating perovskites RMnO3 (R=La,Pr,Nd,...). RMnO3 with a large GdFeO3-type distortion is regarded as a frustrated spin system having ferromagnetic nearest-neighbor and antiferromagnetic (AF) nextnearest-neighbor (NNN) interactions within a MnO2 plane. The staggered orbital order associated with the GdFeO3-type distortion induces the anisotropic NNN interaction, and yields unique sinusoidal and up-up-down-down AF ordered states in the distorted perovskites with e 1 g configuration. and e 1 g t 6 2g configurations, respectively, the e g orbital is doubly degenerate and the t 2g orbital degree of freedom is quenched. It is widely recognized that the layered-type (A-type) antiferromagnetic (AF) structure in LaMnO 3 is understood from the view point of the anisotropic superexchange (SE) interaction under the directional order of orbital [1,2]. On the other hand, the spin structure in nickelates (R =La) is distinct from the A-type AF; the socalled "up-up-down-down"-type one where two Ni sites of "up" spins are followed by two sites of "down" spins along the principal axes in the cubic unit cell. Origin of this unusual magnetic order has been a long-standing question, as well as its relations to metal-insulator transition, orbital order (OO), and charge disproportionation [3][4][5]. Recently, a similar spin structure, i.e. the up-up-down-down order in a MnO 2 plane (E-type AF order in the Wollan-Koehler notation [6]), is found in a manganite, HoMnO 3 [7] with a significantly distorted perovskite structure. This has to be a bridge between the well-understood A-type AF in manganites and the unique magnetic ground state in nickelates.In this Letter, we examine systematically the magnetic and orbital structures in a series of RMnO 3 as a function of the ionic radius (r R ) of R. The most significant effect on the crystal structure by decreasing r R is an enhancement of the cooperative rotation of the MnO 6 octahedra (the GdFeO 3 -type distortion) characterized by the decrease of Mn-O-Mn bond angle φ. Let us first summarize in Fig. 1 the orbital (a) and spin (b) ordering temperatures (T OO and T N , respectively) on Mn sites of RMnO 3 as a function of φ, which is based on both the present and former studies [7][8][9][10]. Here, we adopt the φ at room temperature [11]. The T OO monotonically increases with decreasing r R , while the magnetic transition occurs from the A-type AF to the E-type one through the incommensurate structure. We argue that the combination of OO and next-nearest-neighbor (NNN) SE interaction brings about a nontrivial effect on the magnetic ground state in the systems with the orbital degeneracy and the large GdFeO 3 -type distortion. Microscopic calculation shows that the magnetism in this system is mapped onto the frustrated spin model which well reproduces the phase diagram of RMnO 3 .A series of RMnO 3 (R=La−Dy) crystals were grown by the floating zone method. We made powder x-ray diffraction measurements on th...

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Distorted perovskite witheg1configuration as a frustrated spin system

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“…3 The type of magnetic structure (ferromagnetic vs. antiferromagnetic) of bismuth manganite can be modeled using the Hamiltonian of superexchange interaction: (8) Let us consider the superexchange interaction between nearest neighbor Mn 3+ ions, which depends on orbital states of interacting ions. In contrast to the case of rare earth manganites [11], the orbital states of magnetic neighbors differ in both sign and magnitude. Then, the orbital dependence of the constants of superexchange interaction is as follows: (9) where J 0 = 1.69 × 10 4 K Å…”

Section: Crystalline and Orbital Structures Of Bimnomentioning

confidence: 92%

“…The existence of an orbital structure in BiMnO 3 crystals was theoretically predicted [5][6][7][8]. The ground state wavefunction on each manga nese ion has the following form [11]: (1) where and are the eigenfunctions and Φ n is the angle that characterizes the mixing of eigenfunc tions of the 5 E ground state of the nth ion of trivalent manganese.…”

Section: Crystalline and Orbital Structures Of Bimnomentioning

confidence: 99%

“…This influence is related to the presence of competition between superexchange interactions. In lanthanum manganite [11], where the antiferromagnetic (A type) structure is stable and unambiguous, a change in the mixing angles of orbital functions by several degrees can lead to a similar modification of the exchange parameters, but the type of magnetic ordering will remain unchanged. Φ n *…”

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“…, α = 1.0, β = 4.5 [11], Φ i is the angle of mixing of eigenfunctions of the orbital ground state of Mn 3+ ion with wavefunction (1), r lm is the average distance in the interacting Mn-O pair (lth and mth ions), ϕ lm is the Mn-O-Mn bond angle (with values taken from experimental data [8]), and x, y, z are the orientations of pseudoperovskite lattice axes (directed approximately along the bonds between nearest neighbor manganese ions). Table 5 presents the values of exchange interaction constants calcu lated using the data from Table 4.…”

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Specific features of magnetic structure formation in orbitally degenerate BiMnO3 manganite

Gonchar

Nikitina

Никифоров

2013

J. Exp. Theor. Phys.

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Four‐sublattice ferrimagnetic systems: I. Quantum fluctuations of spins at zero temperature

Qiu

Zhang

2003

Physica Status Solidi (b)

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Within the framework of the linear spin wave approximation, the quantum fluctuations of spins at zero temperature in four-sublattice ferrimagnetic systems are studied by employing retard Green's functions. The effects of exchange constants on the quantum fluctuations of spins are discussed for three different spin-configurations. The magnetic properties of these spin configurations are related to their magnetically structural symmetry. When the parameters of the exchange couplings are adjusted, the crossover of the spin configurations results in the strong quantum fluctuations, owing to the behaviors of the non-threedimensional magnetically system. When two of the four exchange-constants in the present four-sublattice bulk systems are set to be zero, the system behaves as a non-three-dimensionally magnetic system, although the structure of the system is still three-dimensional. All the exchange couplings involve in the quantum competition of the systems, but the effects of antiferromagnetic and ferromagnetic exchange couplings are different evidently. The antiferromagnetic exchange couplings play an important role in a balance of the quantum competition.

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Superexchange interaction in insulating manganitesR1−xAxMnO3<

Cited by 34 publications

References 38 publications

Distorted perovskite witheg1configuration as a frustrated spin system

Distorted perovskite witheg1configuration as a frustrated spin system

Specific features of magnetic structure formation in orbitally degenerate BiMnO3 manganite

Four‐sublattice ferrimagnetic systems: I. Quantum fluctuations of spins at zero temperature

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