ФТТ, 2007, том 49, выпуск 3

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Effect of alkali-earth ions on local structure
of the LaAlO3--La0.67A0.33MnO3 (A=Ca, Sr, Ba) diluted
solid solutions: 27Al NMR studies

E.V.Charnaya, ChengTien\kern1pt*, N.V.Chejina\kern1pt**, M.K.Lee\kern1pt*, S.Y.Sun\kern1pt*

Institute of Physics, St. Petersburg State University, St. Petersburg, Petrodvorets,
198504 Russia
* Department of Physics, National Cheng Kung University, Tainan,
70101 Taiwan
** Department of Chemistry, St. Petersburg State University, St. Petersburg, Petrodvorets,
198504 Russia
E-mail: charnaya@paloma.spbu.ru

(Received May 11, 2006)

27Al Magic Angle Spinning (MAS) NMR was studied for diluted alkali-earth metal doped lanthanum manganite solid solutions in the lanthanum aluminate (1-y)LaAlO3--yLa0.67A0.33MnO3 (A=Ca, Sr, Ba) with y=0,2,3, and 5 mol%. The spectra depended on the dopant species and showed higher substitutional ordering for the Ba containing mixed crystals. Magnetically shifted lines were observed in all solid solutions and were attributed to Al in the octahedral oxygen environment near manganese trivalent ions. Nonlinear dependences of their intensity were referred to the manganese-rich cluster formation. An additional MAS NMR line corresponding to aluminum at sites different from the octahedral site in pure LaAlO3 was observed only in solutions doped with Ba. 3Q MAS NMR revealed the the broadening of this line is governed mainly by quadrupole coupling and allowed calculating the isotropic chemical shift.

The present work was supported by the National Science Council of Taiwan under Grant 93-2811-M-006-021.

PACS: 76.60.-k, 61.66.-f

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