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arXiv · 1206.3813

Magnetic dimers and trimers in the disordered $S=3/2$ spin system BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$

F. A. Garcia·U. F. Kaneko·E. Granado·J. Sichelschmidt·M. Hölzel·J. G. S. Duque·C. A. J. Nunes·R. P. Amaral·P. Marques-Ferreira·R. Lora-Serrano
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Abstract

We report a structural/magnetic investigation by X-ray absorption spectroscopy (XAS), neutron diffraction, dc-susceptibility ($\chi_{\mbox{dc}}$) and electron spin resonance (ESR) of the 12R-type perovskite BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$. Our structural analysis by neutron diffraction supports the existence of structural trimers with chemically disordered occupancy of Mn$^{4+}$ and Ti$^{4+}$ ions, with the valence of the Mn ions confirmed by the XAS measurements. The magnetic properties are explored by combining dc-susceptibility and $X$-band ($9.4$ GHz) electron spin resonance, both in the temperature interval of $2\leq T\leq1000$ K. A scenario is presented under which the magnetism is explained by considering magnetic dimers and trimers, with exchange constants $J_{a}/k_{B}=200(2)$ K and $J_{b}/k_{B}=130(10)$ K, and orphan spins. Thus, BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$ is proposed as a rare case of an intrinsically disordered $S=3/2$ spin gap system with a frustrated ground state.

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F. A. Garcia, U. F. Kaneko, E. Granado, J. Sichelschmidt, M. Hölzel, J. G. S. Duque, C. A. J. Nunes, R. P. Amaral, P. Marques-Ferreira, R. Lora-Serrano. 2012-06-18. Magnetic dimers and trimers in the disordered $S=3/2$ spin system BaTi$_{1/2}$Mn$_{1/2}$O$_{3}$. https://arxiv.org/abs/1206.3813

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