Melting of the orbital order in LaMnO3 probed by NMR

Abstract

The Mn spin correlations were studied near the O'-O phase transition at T{JT} = 750 K, up to 950 K with 17O and 139La NMR in a stoichiometric LaMnO3 crystalline sample. The measured local hyperfine fields originate from the electron density transfered from the eg- and t2g-orbitals to the 2s(O) and 6s(La) orbits, respectively. By probing the oxygen nuclei, we show that the correlations of the Mn spins are ferromagnetic in the ab-plane and robust up to T{JT} whereas along the c-axis, they are antiferromagnetic and start to melt below T{JT}, at about 550 K. Above T{JT} the ferromagnetic Mn-Mn exchange interaction is found isotropic. The room temperature orbital mixing angle, ϕnmr = 109+-1.5°, of the eg ground state is close to the reported value which was deduced from structural data on Jahn-Teller distorted MnO6 octahedra. For T > T{JT} LaMnO3 can be described in terms of non-polarized eg-orbitals since both eg-orbitals are equally occupied.

7 pages, 7 figures

References in corpus (2)

• Origin of Jahn-Teller distortion and orbital-order in LaMnO3
• Computation of correlation-induced atomic displacements and structural transformations in paramagnetic KCuF3 and LaMnO3

Cited by in corpus (6)

• Electronic, structural, and magnetic properties of LaMnO${}_3$ phase transition at high temperature
• Local structure study of the orbital order/disorder transition in LaMnO${}_3$
• Electron-Lattice Interplays in LaMnO3 from Canonical Jahn-Teller Distortion Notations
• Uniaxial pressure induced half-metallic ferromagnetic phase transition in LaMnO${}_3$
• Jahn-Teller induced nematic orbital order in tetragonal Sr${}_2$VO${}_4$
• ESR evidence for partial melting of the orbital order in LaMnO${}_3$ below the Jahn-Teller transition