Crystallography in Material Science

The compositions and purity of polycrystalline powder samples of Nd0.7Sr0.3 Mn1-x MgxO3 (x = 0.0, 0.1, 0.2, 0.3), LaCr1-xMnxO3 (x = 0.0, 0.1, 0.2, 0.3) and La1-x Ndx Cr0.5 Mn0.5 O3 (x = 0.0, 0.15, 0.2) were characterized by X-ray diffraction and chemical analysis. The magnetic properties were investigated by neutron powder diffraction technique and magnetization measurement using a SQUID. All the structures studied have orthorhombic structure, space group Pnma, in a wide range of temperatures. The Mg-substitution in Nd0.7Sr0.3Mn1-xMgxO3 creates only small distortions in the nuclear structure. The magnetic properties of the compounds, however, are significantly affected by Mgsubstitution. All the samples of nominal composition LaCr1-xMnxO3 have orthorhombic structure with space group Pnma at temperatures between 1.5 and 400 K. However, at 600 K, all samples are found to have rhombohedral structure with space group R-3c. The magnetic properties of the system are markedly affected by Mn-substitution. The parent compound, LaCrO3, is purely G-type antiferromagnetic with Neel temperature at about 300 K. With increasing Mnsubstitution, gradually, a ferromagnetic component develops in the system, thereby leading to the occurrence of canted magnetic moment. The magnetic structure of La1-x NdxCr0.5Mn0.5O3 is antiferromagnetic, G-type, from room temperature down to 10 K. A small ferromagnetic component appears at the lowest temperatures.