相界微观相互作用的解：亚稳反铁磁烧绿石Yb $_{2}$ Ge $_{2}$ O $_{7}$的单晶研究
Unravelling competing microscopic interactions at a phase boundary: a single crystal study of the metastable antiferromagnetic pyrochlore Yb$_{2}$Ge$_{2}$O$_{7}$
摘要：
我们报告了我们新合成的结构亚稳反铁磁烧绿石Yb $_{2}$ Ge $_{2}$ O $_{7}$单晶的非弹性中子散射测量。我们确定了四个最小允许的最近邻各向异性交换参数通过配合线性自旋波理论补充配合的高温比热。如此确定的交换参数与为$g$ -张量分量确定的值强烈相关，如先前对相关Yb烧绿石Yb $_{2}$ Ti $_{2}$ O $_{7}$观察到的。为了解决这个问题，我们直接确定的$g$张量从电子顺磁共振的1% Yb掺杂的Lu $_{2}$ Ge $_{2}$ O $_{7}$，从而使交换参数的明确的确定。我们的研究结果表明，Yb $_{2}$ Ge $_{2}$ O $_{7}$非常接近反铁磁$Γ_5$相和张开铁磁相之间的经典相界。通过将我们的结果与最近的Yb $_{2}$ Ti $_{2}$ O $_{7}$的结果并置，我们的工作表明，Yb烧绿石氧化物代表了理想的系统，用于研究接近经典相界的量子磁体。
英文摘要：
We report inelastic neutron scattering measurements from our newly synthesized single crystals of the structurally metastable antiferromagnetic pyrochlore Yb$_{2}$Ge$_{2}$O$_{7}$. We determine the four symmetry-allowed nearest-neighbor anisotropic exchange parameters via fits to linear spin wave theory supplemented by fits of the high-temperature specific heat. The exchange parameters so-determined are strongly correlated to the values determined for the $g$-tensor components, as previously observed for the related Yb pyrochlore Yb$_{2}$Ti$_{2}$O$_{7}$. To address this issue, we directly determined the $g$-tensor from electron paramagnetic resonance of 1% Yb-doped Lu$_{2}$Ge$_{2}$O$_{7}$, thus enabling an unambiguous determination of the exchange parameters. Our results show that Yb$_{2}$Ge$_{2}$O$_{7}$ resides extremely close to the classical phase boundary between an antiferromagnetic $Γ_5$ phase and a splayed ferromagnet phase. By juxtaposing our results with recent ones on Yb$_{2}$Ti$_{2}$O$_{7}$, our work illustrates that the Yb pyrochlore oxides represent ideal systems for studying quantum magnets in close proximity to classical phase boundaries.
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