Magnetic and valent ion states in the real structure of magnetoresistive
manganite-lanthanum perovskites
V.S.Abramov, V.P.Pashchenko, S.I.Khartsev, O.P.Cherenkov
A.A.Galkin Physico-Technical Institute, National Academy of
Sciences of Ukraine, R.Luxembourg st.72, Donetsk, Ukraine
Received May 11, 1998
The influence of manganese-to-lanthanum ratio in manganite-lanthanum
perovskites 1-xMn1+xO3 (0<=x<=0.4)
on the lattice defectness, temperatures of the resistence maxima (Tm)
and magnetoresistive effect (DELTA>R/R0) in
ceramic samples have been studied. The real manganite-lanthanum perovskite
structure has been shown to contain vacansies in both cationic and
anionic sublattices. The defect concentration increases in parallel
with x. The most probable magnetic and valent state of ions
responsible for Tm have been determined theoretically
under account for contributions of the spin and orbital moments of
electron shells and of the nuclear spin moment. A correlation has
been established between the crystal lattice defectness (V(c),
V(a)), magnetic and valent states of ions, Tm
and DELTA*R/R0. A satisfactory agreement has been
found between experimental and theoretical Tm values in
the model of the real imperfect perovskite structure containing vacancies
in both cationic and anionic sublattices and manganese ions of different
valencies in different magnetic and valent states.
Previous | Contents |
Next