Eur. Phys. J. B 28, 75-80 (2002)
https://doi.org/10.1140/epjb/e2002-00202-2

Magnetic interaction in Mg, Ti, Nb doped manganites

¹ Institute of Solid State and Semiconductor Physics of National Academy of Sciences, P. Brovka str. 17, 220072 Minsk, Belarus
² Institute of Physics, Polish Academy of Sciences, al. Lotnikov 32/46, 02-668 Warsaw, Poland
³ 4. Physikalishes Institut der Göttingen Universität, Bunsenstraße 13, 37073 Göttingen, Germany
⁴ Laboratoire CRISMAT, ISMRA, Université de Caen, 6 Boulevard du maréchal Juin, 14050 Caen Cedex, France

Corresponding author: ^a troyan@ifttp.bas-net.by

Received: 24 January 2002
Published online: 9 July 2002

Abstract

An effect of Mn substitution with Me=Mg²⁺, Ti⁴⁺, Nb⁵⁺ in manganites has been investigated by preparing La_0.7Sr_0.3(MnMe_x)O₃ and LaSr_x(MnNb)O₃ series. It was established that substitution of manganese with magnesium up to x=0.16 leads to a collapse of a long-range ferromagnetic order whereas La_0.7Sr_0.3(MnNb)O₃ is ferromagnet with T_C=123 K and exhibits a large magnetoresistance below Curie point despite an absence of four-valent manganese. Hypothetical magnetic phase diagrams are constructed for La_0.7Sr_0.3(MnMe_x)O₃ and LaSr_x(MnNb)O₃. Our results show that Mn³⁺-O-Mn³⁺ exchange interaction is ferromagnetic in the orbitally disordered manganites as well as an increase of Mn⁴⁺ content above 50% from a total amount of manganese ions leads to formation of a spin glass state due to a competition between antiferromagnetic Mn⁴⁺-O-Mn⁴⁺ and ferromagnetic Mn³⁺-O-Mn⁴⁺(Mn³⁺) superexchange interactions.