A study of La_0.6Sr_0.4-xMnTi _xO₃ (x=0.0, 0.05, 0.1, 0.15, and 0.2) manganites with the Ti in B(=Mn)-position and vacancies in A(=La, Sr)-site is presented. The manganites belonged to the rhombohedral phase and small amount of Mn ₃O₄ oxide was observed with increase of Ti content. X-ray adsorption fine structure (XAFS) analysis showed an appearance of Mn ²⁺ ions in perovskite cell and tremendous change of local structure. We suppose that the change of local structure was mainly caused by the appearance of Mn ions in the A-positions and partially by the formation of vacancies in the above position with the increase of x-value. Curie temperature, TC, decreased drastically with x: TC(x=0)=355K and, TC(x=0.05)=185K. Further increase of Ti content changed the low-temperature magnetic state from the ferromagnetic to spin/cluster glass state. Effects of destruction of the eg electron pathway and change of local structure on Curie temperature, caused by the Ti doping, is discussed. © 2005 Elsevier B.V. All rights reserved.

Ulyanov A.N., Yang D.-S., Lee K.-W., Greneche J.-M., Chau N., Yu S.-C.

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Từ khóa : Adsorption; Doping (additives); Glass; Thermal effects; Titanium; X ray analysis; A- and B-site substitution and deficiency; Curie temperature; Local structure; Manganites; Manganese compounds