Neutron diffraction study of crystal and magnetic structure of (La0.7Ca0.3)(1-x)Mn1+xO3 (x=0, 0.1) systems

摘要

The evolution of crystal and magnetic structures of (La0.7Ca0.3)(1-x)Mn1+xO3 (x = 0, 0.1) as a function of temperature was determined. For both compounds the crystal structure is orthorhombic (space group Pnma) with the following sequence of the lattice constants: b/root2 < a < c for x = 0 and c < a < b/root2 for x = 0.1. The para-ferromagnetic transitions at T-c = 265 K for x = 0 and 260 K for x = 0.1 are accompanied by structural distortions. For x = 0 the ferromagnetic ordering of the Mn moments equal to 3.57(10)mu(B) and parallel to the b-axis is stable in the temperature range from 1.5 K to T-c. For x = 0.1 at 1.5 K the magnetic order has two components: the ferromagnetic one with the magnetic moment p = 3.46(12)mu(B) parallel to the b-axis and the antiferromagnetic one with mu = 0.66(23)mu(B) parallel to the c-axis. This order is stable up to T-c = 45 K. Then the ferromagnetic order only exists up to T, = 260 K. These results correlate well with macroscopic magnetic data. At Tc and T, the anomalies in the thermal dependence of Mn-O bond lengths and Mn-O-Mn bond angles are observed. [References: 5]