МАГНІТООПІР А-КАТІОН-ВПОРЯДКОВАНИХ МАНГАНІТІВ В ОБЛАСТІ КІМНАТНИХ ТЕМПЕРАТУР

The A-cation-ordered manganites  are obtained using two-step synthesis. Their chemical composition, crystal structure, magnetic and magnetotransport properties are investigated. It is revealed that the physical properties of the A-cation-ordered manganites  are considerably distinguished from ones of the A-cation-disordered  and strongly depend on the ordering degree of cations  and . So, A-cation-disordered sample is characterized by cubic () unit cell, while the A-cation-ordered one is characterized by tetragonal () cell. The cation states in this system are reversible. The cation-ordered state is stable after the thermal treatment in air up to 1300  0 C. The cation ordring leads to considerable increase of the critical phase transition temperatures. So, the sample  with maximum ordering degree is “metal” below T MI  ~ 311 K, while for the completely disordered one T MI reaches ~ 137 K. Slightly below T MI all the samples display the magnetoresistance peak, which is ~ 10 % and ~ 65 % in field of 9 кOe for the completely ordered and disordered samples, respectively. This important feature, magnetoresistance peak at the room temperatures, determined the potential practical significance of the A-cation-ordered manganites PrBaMn 2 O 6 . The obtained magnetic materials may be used for the elaboration of magnetic field sensors as well as in devices of information storage.