自旋-轨道增强的关联敏感性与非二聚化$4d^4$钛铁矿CdRuO$_3$中的反常磁响应
Spin--orbit-enhanced correlation sensitivity and anomalous magnetic response in non-dimerized $4d^4$ ilmenite CdRuO$_3$
- Tokyo University of Agriculture and Technology（东京农工大学）
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AI总结：
本研究合成并表征了非二聚化钛铁矿CdRuO$_3$，发现自旋-轨道耦合显著增强其关联敏感性，打开约55 meV带隙，并表现出反常的非单调磁响应。
AI中文摘要：
我们报道了CdRuO$_3$的合成与物理性质，这是一种名义上为Ru$^{4+}$ $4d^4$的钛铁矿，具有边共享的RuO$_6$蜂窝状层。粉末X射线衍射确定了晶体学上非二聚化的$R\bar{3}$结构，具有等价的Ru-Ru键和强烈畸变的RuO$_6$环境。压实颗粒的电阻率呈非金属性但非Arrhenius型，而热容包含有限的残余线性项。匹配的非磁性计算表明，不含自旋-轨道耦合的PBE+$U$在$U_{\mathrm{eff}} = 3$ eV之前保持金属性或半金属性，而PBE+SOC+$U$表现出强烈的$U_{\mathrm{eff}}$依赖性，并在$U_{\mathrm{eff}} = 2.5$ eV时于$\Gamma$点打开约55 meV的直接带隙。因此，自旋-轨道耦合显著增强了非立方Ru $t_{2g}$流形的关联敏感性。在扣除稀薄的居里-外斯缺陷贡献后，磁化率仍呈弱非单调性，与普通的泡利响应和独立的纯自旋$S = 1$矩均不一致。因此，CdRuO$_3$实现了钌钛铁矿中预测的非二聚化结构分支，但并非简单的稳健多轨道金属。
英文摘要：
We report the synthesis and physical properties of CdRuO$_3$, a nominal Ru$^{4+}$ $4d^4$ ilmenite with edge-sharing RuO$_6$ honeycomb layers. Powder X-ray diffraction establishes a crystallographically non-dimerized $R\bar{3}$ structure with equivalent Ru-Ru bonds and a strongly distorted RuO$_6$ environment. The compacted-pellet resistivity is nonmetallic but non-Arrhenius, while the heat capacity contains a finite residual linear term. Matched nonmagnetic calculations show that PBE+$U$ without spin-orbit coupling remains metallic or semimetallic up to $U_{\mathrm{eff}} = 3$ eV, whereas PBE+SOC+$U$ exhibits a strong $U_{\mathrm{eff}}$ dependence and opens a direct gap of approximately 55 meV at $Γ$ for $U_{\mathrm{eff}} = 2.5$ eV. Spin-orbit coupling therefore markedly enhances the correlation sensitivity of the non-cubic Ru $t_{2g}$ manifold. After subtraction of a dilute Curie-Weiss defect contribution, the susceptibility remains weakly nonmonotonic and is inconsistent with both an ordinary Pauli response and independent spin-only $S = 1$ moments. CdRuO$_3$ thus realizes the non-dimerized structural branch predicted for ruthenium ilmenites, but not a simple robust multiorbital metal.
