Influence of Oxigen Deficiency on Magnetic, Magnetoresistive and Magnetoelastic Properties of La_(1-x)Sr_xMnO_(3-y) Manganites

摘要

The influence of oxygen deficiency on magnetization, paramagnetic susceptibility, electrical resistivity, magnetoresistance and magnetostriction of La_(1-x)Sr_xMnO_(3-y) (x = 0, 0.2, 0.4; y = 0, 0.13, 0.2) is studied. These properties demonstrate that the ferro - antiferromagnetic magnetic two-phase state are in the oxygen deficiency samples. In samples with y ≠ 0 in lattice sites, in which the oxygen ions are absent, electrons in twos are disposed from maintenance of a crystal electroneutrality. They partially (in x = 0.4, y = 0.13) or fully (in x = 0.4, y = 0.2; x = 0.2, y = 0.13, 0.2) compensate single-charge acceptors (Sr~(2+) ions). In non-compensated donors two electron spins are antiparallel and do not form of the ferromagnetic nanoregions from the s-d exchange gain (ferrons). In sites of lattice with the oxygen vacancies the broken Mn-O-Mn connections present which break the ferromagnetic exchange interactions in them decreasing the middle magnetization in samples with x = 0.2, 0.4 and y = 0.13 and provoking a transition to superparamagnetic behavior in samples with x = 0.2, 0.4 and y = 0.2.