Magnons in the half-doped manganites

Abstract

Recently, based on the refined crystal structure of Pr0.6Ca0.4MnO3 from neutron diffraction, Daoud-Aladine et al.[PRL89,97205(2002)] have proposed a new ground state structure for the half-doped manganites R0.5Ca0.5MnO3, where R is a trivalent ion like Bi,La,Pr,Sm or Y. Their proposal describes the CE magnetic structure attributed to these materials as an arrangement of dimers along the ferromagnetic Mn zig-zag chains that form it. However, the dimers' proposal is in conflict with the Goodenough-Kanamori-Anderson rules, which give a coherent description of many transition metal insulating compounds and predict the coexistence of Mn3+ and Mn4+ ions in equal parts in the half-doped manganites. On the other hand, Rivadulla et al.[PRB 66, 174432 (2002)] have studied several single crystal samples of half-doped manganites and propose a phase diagram in terms of the tolerance factor which contains both types of structures. In the present work we have calculated the magnon dispersion relations for the CE magnetic structure, arising for each type of proposal: the charge ordered and the dimer phases, respectively. We consider a three-dimensional unit cell containing 16 spins, and compare the magnetic excitations along different paths in the first Brillouin zone. We conclude that measurement of the magnon dispersion relations should allow a clear distinction between the two proposals, predicting qualitative differences arising along specific directions of propagation in the first Brillouin zone.

5 pages, 6 figures

References in corpus (5)

• New Type of Charge and Magnetic order in the Ferromagnetic Kondo Lattice
• Ferromagnetic Polarons in La0.5Ca0.5MnO3 and La0.33Ca0.67MnO3
• Island phases and charge order in two-dimensional manganites
• Monte Carlo determination of the phase diagram of the double-exchange model
• Phase Competition in Ln0.5a0.5mno3 Perovskites

Cited by in corpus (6)

• Spin-wave excitations in the ferromagnetic-metallic and in the charge, orbital and spin ordered states in Nd${}_{1-x}$Sr${}_x$MnO${}_3$ with x$\approx$0.5
• Spin Polaron Effective Magnetic Model for La_{0.5}Ca_{0.5}MnO_3
• Correlating Quasi-Electron Relaxation with Quantum Femtosecond Magnetism in the Order Parameter Dynamics of Insulating Manganites
• Spin excitations used to probe the nature of the exchange coupling in the magnetically ordered ground state of Pr${}_{0.5}$Ca${}_{0.5}$MnO${}_3$
• Spin Excitations in Half-Doped Manganites
• Quantum magnons of the intermediate phase of half-doped manganite oxides