CEA-Saclay, IRAMIS/SPEC, F-91191 Gif sur Yvette, France.
J Phys Condens Matter. 2011 Apr 27;23(16):164217. doi: 10.1088/0953-8984/23/16/164217. Epub 2011 Apr 6.
In the pyrochlore Yb(2)GaSbO(7), the Yb(3+) sublattice forms a network of corner sharing tetrahedra and the second sublattice is made up of disordered, non-magnetic Ga(3+) and Sb(5+) ions. We have examined this compound using magnetic susceptibility, (170)Yb Mössbauer spectroscopy (down to 0.03 K) and muon spin relaxation (μSR) (down to 0.02 K) measurements. We establish the size of the Yb(3+) magnetic moments and that of the Yb(3+)-Yb(3+) coupling. At low temperatures, the correlated moments fluctuate between directions that are well tilted relative to the local [111] axis. The lattice disorder does not quench the frustration induced low temperature spin fluctuations but it does remove the first order dynamic transition that is present in the crystallographically ordered counterpart Yb(2)Ti(2)O(7). Below 1.0 K, the fluctuation rate of the correlated moments decreases progressively as the temperature is reduced and the moments remain dynamic down to 0.02 K where the rate is 7 × 10(7) s(-1). Magnetic frustration is operative in Yb(2)GaSbO(7) where the Yb(3+)-Yb(3+) interaction is antiferromagnetic as it is in Yb(2)Ti(2)O(7) where the interaction is ferromagnetic.
在烧绿石 Yb(2)GaSbO(7) 中，Yb(3+)亚晶格形成了由顶角共享四面体组成的网络，而第二个亚晶格由无序的非磁性 Ga(3+)和 Sb(5+)离子组成。我们使用磁化率、(170)Yb Mössbauer 光谱学（低至 0.03 K）和μ子自旋弛豫（μSR）（低至 0.02 K）测量来研究这种化合物。我们确定了 Yb(3+)磁矩的大小以及 Yb(3+)-Yb(3+)耦合的大小。在低温下，相关的磁矩在相对于局部[111]轴倾斜的方向之间波动。晶格无序并没有抑制低温下由受挫诱导的自旋波动，但它确实消除了在晶相有序的 Yb(2)Ti(2)O(7)中存在的一级动力学转变。在 1.0 K 以下，随着温度的降低，相关磁矩的波动速率逐渐降低，磁矩在 0.02 K 时仍保持动态，此时速率为 7×10(7) s(-1)。在 Yb(2)GaSbO(7)中存在磁受挫，其中 Yb(3+)-Yb(3+)相互作用是反铁磁的，就像在 Yb(2)Ti(2)O(7)中相互作用是铁磁的一样。
