Magnetic interaction in Mg, Ti, Nb doped manganites
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 email@example.com
Published online: 9 July 2002
An effect of Mn substitution with Me=Mg2+, Ti4+, Nb5+ in manganites has been investigated by preparing La0.7Sr0.3(MnMex)O3 and LaSrx(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 La0.7Sr0.3(MnNb)O3 is ferromagnet with TC=123 K and exhibits a large magnetoresistance below Curie point despite an absence of four-valent manganese. Hypothetical magnetic phase diagrams are constructed for La0.7Sr0.3(MnMex)O3 and LaSrx(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.
PACS: 75.30.Kz – Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.) / 75.30.Vn – Colossal magnetoresistance / 75.30.Et – Exchange and superexchange interactions
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002