TY - JOUR

T1 - Magnetic structure and double exchange in the La1 − x Ca x MnO3

AU - Karpenko, B. V.

AU - Fal’kovskaya, L. D.

AU - Kuznetsov, A. V.

N1 - This work was supported in part by the Russian Foundation for Basic Research (project no. 06-03-90893 Mol-a), according to the Plan of the Russian Academy of Sciences (project no. 01.2.006 13391) and Program of the Presidium of the Ural Division, Russian Academy of Sciences (New Materials and Structures)

PY - 2008/5/1

Y1 - 2008/5/1

N2 - This paper considers from a theoretical viewpoint the problem of the appearance of different magnetic structures in the series of compounds La1 − x Ca x MnO3, 0 ≤ x ≤ 1. It is assumed that the entire series possesses the structure of the GdFeO3 type. The problem is analyzed in the nearest-neighbor approximation with allowance for direct exchange, double exchange, and anisotropy energy (ten interaction parameters on the whole). The spin operator of double exchange interaction in the crystal between the different-valence ions of manganese Mn3+ and Mn4+ is the direct generalization of two-spin operator in the well-known problem of the Anderson-Hasegawa molecule. The minimization of the energy along the direction angles of magnetic sublattices leads to a set of transcendental equations, whose solutions give eleven types of magnetic configurations: two ferromagnetic, three collinear antiferromagnetic, and six noncollinear antiferromagnetic. As the concentration of calcium ions x changes, one spin configuration changes another as the ground state. The appearance of angular configurations in the system occurs only due to the simultaneous presence of direct Heisenberg interaction and substantially non-Heisenberg double exchange.

AB - This paper considers from a theoretical viewpoint the problem of the appearance of different magnetic structures in the series of compounds La1 − x Ca x MnO3, 0 ≤ x ≤ 1. It is assumed that the entire series possesses the structure of the GdFeO3 type. The problem is analyzed in the nearest-neighbor approximation with allowance for direct exchange, double exchange, and anisotropy energy (ten interaction parameters on the whole). The spin operator of double exchange interaction in the crystal between the different-valence ions of manganese Mn3+ and Mn4+ is the direct generalization of two-spin operator in the well-known problem of the Anderson-Hasegawa molecule. The minimization of the energy along the direction angles of magnetic sublattices leads to a set of transcendental equations, whose solutions give eleven types of magnetic configurations: two ferromagnetic, three collinear antiferromagnetic, and six noncollinear antiferromagnetic. As the concentration of calcium ions x changes, one spin configuration changes another as the ground state. The appearance of angular configurations in the system occurs only due to the simultaneous presence of direct Heisenberg interaction and substantially non-Heisenberg double exchange.

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U2 - 10.1134/S0031918X08050049

DO - 10.1134/S0031918X08050049

M3 - Article

VL - 105

SP - 443

EP - 452

JO - Physics of Metals and Metallography

JF - Physics of Metals and Metallography

SN - 0031-918X

IS - 5

ER -