Abstract

We study 1 isolated or 2 neighboring Mn impurities, as well as 1 Mn and 1, 2, or 3 Mg ions as substitutional impurities for Ga in zinc-blende and wurtzite supercells of GaN by means of density functional calculations. Taking into account the electron correlation in the local spin density approximation with explicit correction of the Hubbard term (the LSDA+U method) and full lattice relaxation we determine the nearest neighbor exchange J for a pair of Mn impurities. We find J to be ferromagnetic and in between 9 and 17 meV in the Hamiltonian \(\hat{H}=-2 J \hat{\vec{S}}_1\cdot \hat{\vec{S}}_2\) for the different lattices. That J is only weakly influenced by the U parameter (varying between 2 and 8 eV). From a detailed analysis of the magnetization density distribution we get hints for a ferromagnetic super-exchange mechanism. Also the Mn valence was found to be 3+ in the absence of co-doping with Mg. Co-doping with Mg leads to a valence change to 4+ for 1 Mg and to 5+ for 2 Mg, independently whether the Mn and Mg ions are close or far from each other. We show that the valence change can already be concluded from a careful analysis of the density of states of GaN doped with Mn without any Mg.

Graphical abstract

中文翻译：

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掺锰和掺镁的GaN中的交换耦合和Mn化合价

摘要

我们通过密度泛函计算研究了GaN闪锌矿和纤锌矿超级电池中Ga的1个分离的或2个相邻的Mn杂质，以及1 Mn和1、2或3 Mg离子作为Ga的替代杂质。考虑到在用Hubbard项进行显式校正（LSDA + U方法）和完全晶格弛豫的情况下，在局部自旋密度近似中的电子相关性，我们确定了一对Mn杂质的最近邻位交换J。我们发现哈密​​顿量\（\ hat {H} =-2 J \ hat {\ vec {S}} _ 1 \ cdot \ hat {\ vec {S}} _ 2 \中的J是铁磁性的，且介于9和17 meV之间）用于不同的晶格。也就是说Ĵ仅微弱由影响ù参数（在2到8 eV之间变化）。通过对磁化密度分布的详细分析，我们可以获得铁磁超交换机制的提示。另外，在不与Mg共掺杂的情况下，发现Mn价为3+。与Mg共掺杂会导致1 Mg的化合价变为4 +，2 Mg的化合价变为5+，无论Mn和Mg离子彼此接近还是远离。我们表明，通过仔细分析掺有Mn且不含Mg的GaN的态密度，已经可以得出化合价变化。

图形概要