Magnesium substitution in Nd0.7Sr0.3MnO3

Magnesium substitution in Nd_0.7Sr_0.3MnO₃ has been studied by neutron powder diffraction. Polycrystalline samples of nominal compositions Nd_0.7Sr_0.3Mn_1−yMg_yO₃ with y=0.0, 0.1, 0.2 and 0.3 were synthesized by the standard solid-state reaction method. Rietveld refinements of the neutron powder diffraction data showed that all samples had distorted perovskite structure of orthorhombic symmetry. Mg initially preferred to substitute for Nd and only at Mg concentration greater than 0.1, a substantial substitution for Mn occurred. Our study also showed that Mg-substitution did not change the crystal structure of Nd_0.7Sr_0.3MnO₃.     

Effect of composition on structural and magnetic properties of nanocrystalline Ni0.8−xZn0.2MgxFe2O4 ferrite

Nanocrystalline magnetic particles of Ni_0.8−xZn_0.2Mg_xFe₂O₄ ferrites with x lying between 0.0 and 0.8 were synthesized using metal nitrates and freshly extracted egg-white. The synthesized powders were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and transmission electron microscopy (TEM). With increasing magnesium concentration, the lattice constant increases while X-ray density decreases. The average crystallite size determined from XRD data using Scherrer formula lie in the range of 35–59 nm. TEM image shows spherically agglomerated particles with average crystallite size agreed well with that obtained from XRD. Magnetic properties measured at room temperature by vibrating sample magnetometer (VSM) reveal a decrease in saturation magnetization up to Mg content of 0.6. In agreement with FT-IR results, the unexpected increase in the magnetization at Mg content of 0.8 can be attributed to the tendency of Mg²⁺ ions to occupy the tetrahedral site. The decrease in the value of coercivity with increasing magnesium content can be explained based on the magneto-crystalline anisotropy.     

LaMn1-xMgxO3钙钛矿的低温磁性

采用乙二胺四乙酸-柠檬酸联合溶胶凝胶法合成了B位掺镁的简单钙钛矿纯相样品LaMn1-xMgxO3(x=0~0.50). Mg在钙钛矿B位的掺杂和调节Mn3+/Mn4+的摩尔比强烈地影响样品的磁性行为. x≤0.08时, 样品低温下表现弱的铁磁性; x≥0.18时, 随着Mg掺杂引入的Mn4+离子间的反铁磁性超交换作用与Mn3+-Mn4+离子间的铁磁性双交换作用使样品在低温下呈现自旋玻璃态. 随着Mg2+掺杂量的增加, 样品的磁有序温度与自旋凝固温度单调降低.