稀Yb：YAlO $_3$中磁性二聚体的实验观察
Experimental observation of magnetic dimers in diluted Yb:YAlO$_3$
摘要：
通过比热、磁化强度和高分辨率非弹性中子散射（INS）测量，对Yb $_{0.04}$ Y $_{0.96}$ AlO $_3$（Yb掺杂YAP）YAlO $_3$）中Yb磁性二聚体进行了全面的实验研究。在我们的样品中，Yb离子随机分布在晶格上，并且由于沿$c$轴的最近邻反铁磁耦合，Yb离子的$\sim 7$ \%形成量子二聚体。在零场，二聚体的形成表现在一个外观的非弹性峰在$Δ\approx 0.2$ ~meV的INS光谱和肖特基的比热异常。INS峰的结构因子沿$L$方向呈现余弦调制，与$c$轴最近邻二聚体内耦合一致。对低温比热的仔细拟合表明，激发态是简并三重态，这表明尽管低晶体对称性和各向异性磁偶极子贡献，但有效的Yb-Yb交换相互作用的各向异性令人惊讶地小，与Yb母体化合物YbAlO $_3$ [arXiv：1904.11513，arXiv：1902.04112]的先前报道一致，与Yb $_2$ Pt $_2$ Pb [arXiv：1606.01309，arXiv：1907.01067]相反。Yb二聚体的分析计算精确地再现了所获得的结果。
英文摘要：
We present a comprehensive experimental investigation of Yb magnetic dimers in Yb$_{0.04}$Y$_{0.96}$AlO$_3$, an Yb-doped Yttrium Aluminum Perovskite (YAP) YAlO$_3$ by means of specific heat, magnetization and high-resolution inelastic neutron scattering (INS) measurements. In our sample, the Yb ions are randomly distributed over the lattice and $\sim 7$\% of Yb ions form quantum dimers due to nearest-neighbor antiferromagnetic coupling along the $c$-axis. At zero field, the dimer formation manifests itself in an appearance of an inelastic peak at $Δ\approx 0.2$~meV in the INS spectrum and a Schottky-like anomaly in the specific heat. The structure factor of the INS peak exhibits a cosine modulation along the $L$ direction, in agreement with the $c$-axis nearest-neighbor intra-dimer coupling. A careful fitting of the low-temperature specific heat shows that the excited state is a degenerate triplet, which indicates a surprisingly small anisotropy of the effective Yb-Yb exchange interaction despite the low crystal symmetry and anisotropic magnetic dipole contribution, in agreement with previous reports for the Yb parent compound, YbAlO$_3$ [arXiv:1904.11513, arXiv:1902.04112], and in contrast to Yb$_2$Pt$_2$Pb [arXiv:1606.01309, arXiv:1907.01067]. The obtained results are precisely reproduced by analytical calculations for the Yb dimers.
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