Theoretical study on the spin and orbital orderings in Ruddlesden-Popper compound La_3-3xCa_1+3xMn₃O₁₀(0 ≤ x ≤ 1)

Abstract

In this paper, the spin and orbital orderings of the n = 3 Ruddlesden-Popper (RP) series of compounds La_3-3xCa_1+3xMn₃O₁₀ have been analyzed theoretically for the whole doping range 0 ≤ x ≤ 1, the calculation is based on the unrestricted Hartree-Fock approximation and the real-space recursion method. In agreement with experimental observations, we find that the ground state of La_3-3xCa_1+3xMn₃O₁₀ is ferromagnetic metal at x=0.3 and is G-type antiferromagnetic insulator at x = 1. The ferromagnetic metallic state is sustained for lower doping range 0 ≤ x < 0.39; while for the wide middle doping range 0.39 < x < 0.96, A-type antiferromagnetic metal and ferromagnetic metal compete strongly with each other, they are finally replaced by G-type antiferromagnetically ordered state when x > 0.96. Our study unveils a strong spin-orbital correlation in the ferromagnetic metallic state for doping range 0 ≤ x < 0.39, an orbital ordering transition takes place at x = 0.06 which changes from the nearest-neighbor antiferro-orbital ordering (0 ≤ x < 0.06) to the layer-type antiferro-orbital ordering (0.06 < x < 0.39).