ФТП, 2007, том 41, выпуск 5

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Microstructure evolution and magnetoresistance of the A-site ordered Ba-doped manganites

S.V.Trukhanov\kern1pt, L.S.Lobanovski, M.V.Bushinsky, V.A.Khomchenko,
V.V.Fedotova, I.O.Troyanchuk, H.Szymczak\kern1pt*

Joint Institute of Solids and Semiconductor Physics, National Academy of Sciences of Belarus,
220072 Minsk, Belarus
* Institute of Physics, Polish Academy of Sciences,
02-668 Warsaw, Poland

(Получена 12 сентября 2006 г. Принята к печати 3 октября 2006 г.)

The microstructure, crystal structure and magnetotransport properties of the microsized and nanosized Ba-doped manganites have been investigated. \glqq Two-step\grqq reduction-reoxidation procedure has been used to obtain nanosized ceramic manganite Nd0.70Ba0.30MnO3 (II). The parent microsized manganite Nd0.70Ba0.30MnO3 (I) have been prepared by usual ceramic technology in air. Then the sample has been annealed in vacuum. The grain size of the reduced sample, determined by scanning electron microscopy, decreased from ~ 5 mum down to ~ 100 nm. To obtain the oxygen stoichiometry nanosized sample, the Nd0.70Ba0.30MnO2.60 has been again annealed in air. It is established that the (I) sample is a pseudocubic perovskite whereas (II) --- a tetrahedral as consequence of Nd3+ and Ba2+ ions as well as oxygen vacancies ordering. The (I) sample is ferromagnet with TC~ 140 K. It has metal-insulator transition at TMI~ 135 K and peak of magnetoresistance ~ 50% in field of 9 kOe. For the (II) sample the critical points of phase transitions move to higher temperatures, TC~ 320 K and TMI~ 310 K. The magnetoresistance of the (II) sample at the room temperature (T~ 293 K) is about 7% in field of 9 kOe. The magnetotransport properties are interpreted in frame of nanosized effect.

PACS: 75.30.Et, 75.30.Vn, 75.50.Lk

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