反铁磁莫特绝缘体Ca$_3$(Ru$_{0.99}$Ti$_{0.01}$)$_2$O$_7$中的磁场驱动相切换
Magnetic field-driven phase switching in the antiferromagnetic Mott insulator Ca$_3$(Ru$_{0.99}$Ti$_{0.01}$)$_2$O$_7$
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中文总结 AI 辅助
研究通过Ru位点等价替代实现Ca$_3$(Ru$_{1 - x}$Ti$_x$)$_2$O$_7$的带宽控制反铁磁莫特绝缘相，系统研究其磁场诱导相切换，揭示了该化合物的磁$H$ - $T$相图，发现其与典型反铁磁体相图相似但临界场重整化。
中文摘要 AI 辅助
通过在Ru位点进行等价替代，在Ca$_3$(Ru$_{1 - x}$Ti$_x$)$_2$O$_7$中实现了带宽控制的反铁磁莫特绝缘相。对于仅1% Ti的稀替代，莫特绝缘体基态与原始Ca$_3$Ru$_2$O$_7$的基态几乎简并，其中Ru磁矩在反铁磁方式堆叠的金属RuO$_2$双层内铁磁排列。这种掺杂化合物异常浅的自由能景观源于电子 - 电子和电子 - 晶格相互作用的交织。我们系统研究了Ca$_3$(Ru$_{0.99}$Ti$_{0.01}$)$_2$O$_7$中磁场诱导的相切换以探索其磁$H$ - $T$相图。沿易$b$轴施加磁场时，磁化强度在约6 T处表现出一阶自旋翻转转变，电阻降低但自旋翻转相仍绝缘。高于10.5 T时，所有Ru磁矩与$b$轴对齐，形成强制铁磁金属相。沿$a$轴施加磁场时，高达14 T未观察到自旋翻转或强制铁磁相。电子动能和电子 - 晶格耦合影响系统自由能平衡，所得$H$ - $T$相图虽临界场大幅重整化，但仍与典型各向异性反铁磁体的相图非常相似。
英文摘要
A bandwidth-controlled antiferromagnetic Mott-insulating phase in Ca$_3$(Ru$_{1-x}$Ti$_x$)$_2$O$_7$ is realized through isovalent substitution at the Ru site. For a dilute substitution with only 1% Ti, the Mott insulator ground state remains nearly degenerate with the ground state of pristine Ca$_3$Ru$_2$O$_7$, where the Ru moments are ferromagnetically aligned within the metallic RuO$_2$ bilayers stacked in an antiferromagnetic fashion. The exceptionally shallow free energy landscape of this doped compound arises from intertwined electron-electron and electron-lattice interactions. This makes its magnetic and transport properties highly sensitive to external perturbations. We systematically investigated magnetic-field-induced phase switching in Ca$_3$(Ru$_{0.99}$Ti$_{0.01}$)$_2$O$_7$ to explore its magnetic $H$-$T$ phase diagram. With the field applied along the easy $b$-axis, parallel to the antiferromagnetic moments, the magnetization exhibits a first-order spin-flop transition at $\approx $ 6 T, indicating reorientation of the Ru moments perpendicular to the field. The transition is accompanied by a decrease in the electrical resistance, but the spin-flop phase remains insulating. Above 10.5 T, all Ru moments align with the $b$-axis, resulting in a forced ferromagnetic metallic phase. In contrast, neither spin-flop nor forced-ferromagnetic phases are observed up to 14 T, when the field is applied along the $a$-axis. While the electronic kinetic energy and the electron-lattice coupling contribute to the free-energy balance of this system, the resulting $H$-$T$ phase diagram is remarkably simple and closely resembles that of a canonical anisotropic antiferromagnet, albeit with substantially renormalized critical fields.
