Eur. Phys. J. B 42, 51-61 (2004)
https://doi.org/10.1140/epjb/e2004-00357-8

Influence of oxygen vacancies on the magnetic and electrical properties of La_1-xSr_xMnO_3-x/2 manganites

¹ Institute of Solids and Semiconductor Physics, National Academy of Sciences of Belarus, P. Brovka str. 17, 220072 Minsk, Belarus
² Laboratoire CRISMAT, ISMRA, 6 Boulevard du Maréchal Juin 14050 Caen Cedex, France
³ Institute of Physics, Polish Academy of Sciences, Lotnikov str. 32/46, 02-668 Warsaw, Poland

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

Received: 30 April 2004
Revised: 14 July 2004
Published online: 26 November 2004

Abstract

The crystal structure, magnetization and electrical transport depending on the temperature and magnetic field for the doped stoichiometric as well as anion-deficient () ortomanganite systems have been experimentally studied. It is established that the stochiometric samples in the region of the are an -orthorhombic perovskites whereas in the  – a rhombohedric. For the anion-deficient system the symmetry type of the unit cell is similar to the stoichiometric one. As a doping level increases the samples in the ground state undergo a number of the magnetic transitions. It is assumed that the samples with the large amount of oxygen vacancies are a cluster spin glasses () and temperature of the magnetic moment freezing is ~40 K. All the anion-deficient samples are semiconductors and show considerable magnetoresistance over a wide temperature range with a peak for the x = 0.175 only. Concentration dependences of the spontaneous magnetization and magnetic ordering temperature for the anion-deficient  system have been established by the magnetic measurements and compared with those for the stoichiometric one. The magnetic propeprties of the anion-deficient samples may be interpreted on the base of the superexchange interaction and phase separation (chemical disorder) models.