Evolution of crystal structure with the oxygen content in the LaMn0.9Cr0.1O3+δ (3.00 ≤ 3+δ ≤ 3.12) compound

We report the structural evolution as a function of oxygen content for LaMn0.9Cr0.1O3+delta(3.00 less than or equal to 3 + delta less than or equal to 3.12) in samples prepared with accurate control of the oxygen content. The relationship between the structural parameters and magnetic behavior is established using 6 as control parameter. As the 6 value increases, three different orthorhombic regions are found: for delta < delta(c), the distorted O' phase (b/root2 < c < a), and for delta > 0.06 two low distorted orthorhombic regions (O" with b/root2 < a < c and O" ' with a < b/root2 < c). The structural study shows a critical phi(c) approximate to 11degrees tilt angle corresponding to delta(c) approximate to 3.06 and is related to a jump in the critical temperature and magnetic moment (mu). This phi(c) separates FM from non-FM samples. The results are compared with those for LaMnO3+delta. The variation of p as a function of oxygen content and therefore with the amounts of Mn4+ allowed us to discuss the role of the Cr3+ ion on the magnetic behavior of LaMn0.9Cr0.1O3+delta. (C) 2002 Elsevier Science (USA). All rights reserved.