We employ density-functional theory (DFT) in the generalized gradient approximation (GGA) and its extensions GGA+$U$ and GGA+Gutzwiller to calculate the magnetic exchange couplings between pairs of Mn ions substituting Cd in a CdTe crystal at very small doping. DFT(GGA) overestimates the exchange couplings by a factor of three because it underestimates the charge-transfer gap in Mn-doped II-VI semiconductors. Fixing the nearest-neighbor coupling $J_1$ to its experimental value in GGA+$U$, in GGA+Gutzwiller, or by a simple scaling of the DFT(GGA) results provides acceptable values for the exchange couplings at 2nd, 3rd, and 4th neighbor distances in Cd(Mn)Te, Zn(Mn)Te, Zn(Mn)Se, and Zn(Mn)S. In particular, we recover the experimentally observed relation $J_4>J_2,J_3$. The filling of the Mn 3$d$-shell is not integer which puts the underlying Heisenberg description into question. However, using a few-ion toy model the picture of a slightly extended local moment emerges so that an integer $3d$-shell filling is not a prerequisite for equidistant magnetization plateaus, as seen in experiment.
Magnetic Properties and Electronic Configurations of Mn Ions in the Diluted Magnetic Semiconductor Ba$_{1-x}$K$_{x}$(Zn$_{1-y}$Mn$_{y}$)$_{2}$As$_{2}$ Studied by X-ray Magnetic Circular Dichroism and Resonant Inelastic X-ray Scattering
用X射线磁圆二色性（XMCD）和Mn $L_{2,3}$边的共振非弹性X射线散射（RIXS）研究了新稀磁半导体Ba $_{1-x}$ K $_{x}$（Zn $_{1-y}$ Mn $_{y}$）$_{2}$ As $_{2}$的磁性和电子激发.对XMCD谱的求和规则分析得到了$0.45μ_{\text{B}}$ /Mn的净自旋矩和$0.05μ_{\text{B}}$ /Mn的小轨道矩。这表明Mn原子处于$d^{5}$的高自旋构型中，而Mn离子之间存在竞争的铁磁和反铁磁相互作用降低了净自旋矩。RIXS光谱显示从1至6 eV能量损失的宽峰，其源自Mn离子的$d$-$d$晶场激发。通过与Ga $_{1-x}$ Mn $_{x}$ As的RIXS谱线形状的比较，我们认为Ba $_{1-x}$ K $_{x}$中Mn的基态（Zn $_{1-y}$ Mn $_{y}$）$_{2}$由于$_{2}$不仅由电荷转移的$3d^{5}\underline{L}$电子构型组成，（$\underline{L}$：配体空穴）具有如Ga $_{1-x}$ Mn $_{x}$ As中的弱结合空穴，但也具有具有自由空穴的纯$3d^{5}$构型。
Ba$_{3}$M$_{x}$Ti$_{3-x}$O$_{9}$(M = Ir, Rh): A family of 5\textit{\textcolor{black}{d}}/4\textit{\textcolor{black}{d}}-based, diluted quantum spin liquids
我们报道了4} \textit{\textcolor{black}{d }} \textcolor{black}{(M = Rh) based and 5} \textit{\textcolor{black}{d }} \textcolor{black}{(M = Ir) based systems Ba$_{3}$M$_{x}$Ti$_{3-x}$O$_{9}$ (nominally $x$ = 0.5, 1). The studied compositions were found to crystallize in a hexagonal structure with the centrosymmetric space group } $P6_{3}/mmc$的结构和磁性。\textcolor{black}{{} The structures comprise of A$_{2}$O$_{9}$ polyhedra (with the A site (possibly) statistically occupied by M and Ti) in which pairs of transition metal ions are stacked along the crystallographic } \textit{\textcolor{black}{c}} \textcol…
Re-examination of electronic structure of dilute Kondo transition-metal ions substituted into a Heavy Fermion compound
Waseda University（早稻田大学）；University of Tokyo（东京大学）；National Institutes for Quantum Science and Technology（量子科学技术研究开发机构）；Japan Synchrotron Radiation Research Institute（日本同步辐射研究所）；Kumamoto University（熊本大学）
Indication of antiferromagnetic interaction between paramagnetic Co ions in the diluted magnetic semiconductor Zn$_{1-x}$Co$_{x}$O
采用X射线磁性圆二色性（XMCD）技术研究了ZnO（0001）衬底上不同氧分压下同质外延生长的Zn $_{1-x}$ Co $_x$ O（$x=0.07$和0.10）薄膜在Co $2p$芯能级吸收边的磁性.吸收光谱的线形在所有的膜中是相同的，并且表明Co $^{2+}$离子取代了Zn位点。的磁场和温度的XMCD强度的依赖性是一致的磁化强度测量，表明除了钴有没有额外的来源的磁矩，并证明在同质外延Zn $_{1-x}$ Co $_{x}$ O薄膜的顺磁和铁磁成分的共存，相反，在异质外延Zn $_{1-x}$ Co $_{x}$ O薄膜的铁磁性先前研究。利用Curie-Weiss定律对XMCD的强度进行了分析，发现顺磁性Co离子之间存在反铁磁相互作用。缺失的XMCD强度和磁化强度信号表明，大多数的Co离子是非磁性的，可能是因为它们是强耦合的反铁磁彼此。在高真空中退火降低了顺磁和铁磁信号。我们将还原归因于Zn $_{1-x}$ Co $_{x}$ O中Co离子与反铁磁纳米团簇的热扩散和聚集。
X-ray Anomalous Scattering of Diluted Magnetic Oxide Semiconductors: Possible Evidence of Lattice Deformation for High Temperature Ferromagnetism
我们研究了在金红石型和金红石型Ti_{1-x} $Co$ _{x} $O$ _{2-delta} $ thin films that exhibit room-temperature ferromagnetism. Intensities of the x-ray Bragg reflection from the films were measured around the $ K $-absorption-edge of Co. If the Co ions randomly substitute on the Ti sites, the intensity should exhibit an anomaly due to the anomalous dispersion of the atomic scattering factor of Co. However, none of the anatase and rutile samples did exhibit an anomaly, unambiguously showing that the Co ions in Ti$ _{1-x} $Co$ _{x} $O$ _{2-delta} $ are not exactly located at the Ti sites of TiO$ _2 $. The absence …
Local atomic and magnetic structure of dilute magnetic semiconductor (Ba,K)(Zn,Mn)$_2$As$_2$
通过对含温X射线和中子全散射数据的原子和磁对分布函数分析，研究了稀磁半导体系统（Ba，K）（Zn，Mn）$_2$ As $_2$的原子和磁结构.我们检测到的曲率变化的温度依赖性的平均tetraxite晶体结构的晶胞体积的温度与铁磁秩序的发病相一致。我们还观察到存在一个定义良好的本地正交结构上的短长度尺度的$\lesssim 5$的，导致在一个相当不对称的本地环境的Mn和As离子。最后，磁性PDF揭示了Mn自旋沿晶体学$c$轴的铁磁排列，具有甚至在铁磁有序温度以上存在的鲁棒最近邻铁磁相关性。我们讨论了这些结果的背景下，其他实验和理论研究这个系统。
