According to density functional theory of first-principles calculation theory, we study systematically the structure, magnetism, electronic and optical properties of Mn-doped LiNbO3. The enthalpies of formation of LiNbO3, when substituting Li and Nb with Mn, are −8.340 and −8.0062 eV/atom, respectively. This means that the LiNbO3 after substitution of Li with Mn is more stable than that of Nb with Mn. And the magnetic moments of LiNbO3 in the substitution of Li with Mn is higher than that in substitution of Nb with Mn. Results of the density of states calculation show that the magnetism comes from Mn atom, and its magnetic moments is 4.3 µB. The rest of the magnetic moments may come from the contribution of the O and Nb atoms, because of the interactions of Mn-3d orbit with the O-2p and Nb-4d orbits. Optical absorption spectra show an improved optical response in the visible range in LiNbO3 by substituting Li with Mn. Results of analysis of oxygen vacancy in LiNbO3 show that oxygen vacancy can improve the magnetic moments of Mn-doped LiNbO3 system.%采用基于密度泛函理论和局域密度近似的第一性原理分析了Mn掺杂LiNbO3晶体的结构,磁性,电子特性和光吸收特性.文中计算了Mn占据Li位和Nb位体系的形成焓,对应的形成焓分别为−8.340 eV/atom和−8.0062 eV/atom,也就意味着Mn 原子优先占据Li位.这也就意味着Mn原子占据Li位的掺杂LiNbO3晶体结构更稳定.磁性分析的结果显示,其对应磁矩也比占据Nb位的高.进一步分析磁性的来源,自旋态密度结果显示： Mn掺杂LiNbO3晶体的磁性主要源于掺杂原子Mn, Mn原子携带的磁矩高达4.3µB,显示出高自旋结构.由于Mn-3d与近邻O-2p及次近邻Nb-4d轨道的杂化作用,计算表明：诱导近邻O原子及次近邻Nb原子产生的磁矩对总磁矩的贡献较小.通过光学吸收谱的分析,得出在可见光区Li位被Mn原子替代以后显示出更好的光吸收响应相比于Nb位.本文还分析了O空位对于LiNbO3晶体磁性与电子性质的影响,结果显示O空位的存在可以增加Mn掺杂LiNbO3体系的磁性.
展开▼
