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A 55Mn NMR study of La0.33Nd0.33Ca0.34MnO3 with 16O and 18O

D. Rybicki 2Czesław Kapusta 2P. C. Riedi 3C. J. Oates 2M. Sikora 2D. Zając 2J. M. De Teresa 1C. Marquina 1M. R. Ibarra 1

1. Universidad de Zaragoza-CSIC, Facultad de Ciencias, Pedro Cerbuna 12, Zaragoza 50009, Spain
2. AGH University of Science and Technology (AGH), al. Mickiewicza 30, Kraków 30-059, Poland
3. University of St. Andrews, School of Physics and Astronomy, St. Andrews KY16 9SS, United Kingdom


This report presents a 55Mn NMR study of 16O and 18O containing La0.33Nd0.33Ca0.34MnO3. Previous bulk measurements reported in the literature reveal that at low temperatures the 16O based compound shows charge ordered (CO) and ferromagnetic (FM) insulating phases, whereas the 18O based compound exhibits a charge ordered insulating behavior [1]. In both compounds, application of a magnetic field can change the low temperature state to a metallic one and the field required for inducing the transitions is two times higher for 18O based compounds. The 55Mn spin-echo spectra were measured at 4.2K. The spectra, for both compounds, consist of a single line corresponding to the double exchange (DE) state of manganese, which is attributed to the existence of ferromagnetic metallic (FMM) regions. The intensity of the resonant line is more than an order of magnitude lower for the 18O based compound compared with the 16O based compound, which indicates an order of magnitude lower content of the FMM phase in the 18O based compound. The Mn resonance of the CO or FM insulating phases are not observed, possibly due to a fast nuclear relaxation of the Mn3+ and Mn4+ cations. The measurements of the spectra for large pulse spacing show a pronounced minimum at the centre of the DE line. This is related to a minimum of the spin-spin relaxation time at the line centre caused by the Suhl-Nakamura interaction between nuclear spins. This interaction is effective in the large regions of uniform magnetisation, which indicates that the FMM regions are at least tens of nanometres in size for both compounds. The results are discussed in terms of phase segregation in the compounds and the influence of oxygen isotopic substitution on it.

[1] M.R.Ibarra et al, Phys. Rev. B, 57 (1998) 7446


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Presentation: poster at E-MRS Fall Meeting 2003, Symposium D, by Damian D. Rybicki
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-27 17:57
Revised:   2009-06-08 12:55