Effect of the A-site randomness on magnetotransport properties of PrBaMn2O6 manganites.
|Sergei Trukhanov 1, Igor Troyanchuk 1, Aleksey Trukhanov 2, Henryk Szymczak 3|
1. The Institute of Solid State & Semiconductor Physics, National Academy of Science of Belarus, 17 P.Brovka, Minsk 220072, Belarus
A-site ordered manganites of the PrBaMn2O6 system have been obtained using a two-step synthesis and characterized with respect to the chemical composition, crystal structure, magnetic and magnetotransport properties. The physical properties of the A-site ordered PrBaMn2O6 manganites obtained using this method significantly differ from the properties of A-site disordered Pr0.50Ba0.50MnO3 synthesized by means of the conventional ceramic technology and depend on the degree of ordering of the Pr3+ and Ba2+ cations. In particular, the A-site disordered Pr0.50Ba0.50MnO3 has a cubic perovskite-like unit cell, while A-site ordered PrBaMn2O6 has a tetragonal unit cell. Cation states in the system under study are reversible. The A-site ordered PrBaMn2O6 state remains stable upon heating in an oxidizing medium up to 1300 0C. The ordering of the Pr3+ and Ba2+ cations leads to a significant increase in the critical temperatures of phase transitions. In particular, PrBaMn2O6 with the maximum degree of ordering is a metallic ferromagnet with the Curie temperature TC ~ 320 K, whereas TC of a fully disordered sample is on the order of 140 K. The samples with intermediate degrees of ordering contain two magnetic phases. Slightly below TC, all such samples exhibit a metal-insulator transition and a peak of the magnetoresistance, which amounts to approximately 10 and 65 % in a magnetic field of 9 kOe for the fully ordered PrBaMn2O6 and disordered Pr0.50Ba0.50MnO3 , respectively. The results are interpreted in terms of the Goodenough-Kanamori empirical rules for indirect exchange interactions with allowance for the degree of ordering of the Pr3+ and Ba2+ cations.
Presentation: Poster at E-MRS Fall Meeting 2006, Symposium C, by Sergei Trukhanov
See On-line Journal of E-MRS Fall Meeting 2006
Submitted: 2006-05-12 12:43 Revised: 2009-06-07 00:44