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arXiv · 1303.3112

Melting of the orbital order in LaMnO3 probed by NMR

A. Trokiner·S. Verkhovskii·A. Gerashenko·Z. Volkova·O. Anikeenok·K. Mikhalev·M. Eremin
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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, {\phi}nmr = 109+-1.5{\deg}, 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.

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A. Trokiner, S. Verkhovskii, A. Gerashenko, Z. Volkova, O. Anikeenok, K. Mikhalev, M. Eremin. 2013-03-13. Melting of the orbital order in LaMnO3 probed by NMR. https://doi.org/10.1103/physrevb.87.125142

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