Sibille Romain, Lhotel Elsa, Ciomaga Hatnean Monica, Nilsen Gøran J, Ehlers Georg, Cervellino Antonio, Ressouche Eric, Frontzek Matthias, Zaharko Oksana, Pomjakushin Vladimir, Stuhr Uwe, Walker Helen C, Adroja Devashibhai T, Luetkens Hubertus, Baines Chris, Amato Alex, Balakrishnan Geetha, Fennell Tom, Kenzelmann Michel
Laboratory for Scientific Developments and Novel Materials, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland.
Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232, Villigen PSI, Switzerland.
Nat Commun. 2017 Oct 12;8(1):892. doi: 10.1038/s41467-017-00905-w.
The charge ordered structure of ions and vacancies characterizing rare-earth pyrochlore oxides serves as a model for the study of geometrically frustrated magnetism. The organization of magnetic ions into networks of corner-sharing tetrahedra gives rise to highly correlated magnetic phases with strong fluctuations, including spin liquids and spin ices. It is an open question how these ground states governed by local rules are affected by disorder. Here we demonstrate in the pyrochlore TbHfO, that the vicinity of the disordering transition towards a defective fluorite structure translates into a tunable density of anion Frenkel disorder while cations remain ordered. Quenched random crystal fields and disordered exchange interactions can therefore be introduced into otherwise perfect pyrochlore lattices of magnetic ions. We show that disorder can play a crucial role in preventing long-range magnetic order at low temperatures, and instead induces a strongly fluctuating Coulomb spin liquid with defect-induced frozen magnetic degrees of freedom.Experimental studies of frustrated spin systems such as pyrochlore magnetic oxides test our understanding of quantum many-body physics. Here the authors show experimentally that TbHfO may be a model material for investigating how structural disorder can stabilize a quantum spin liquid phase.
表征稀土烧绿石氧化物的离子和空位的电荷有序结构，是研究几何受挫磁性的一个模型。磁性离子组织成角共享四面体网络，产生了具有强烈涨落的高度相关磁相，包括自旋液体和自旋冰。由局部规则支配的这些基态如何受到无序影响，这是一个悬而未决的问题。在此，我们在烧绿石TbHfO中证明，向缺陷萤石结构的无序转变附近转化为可调节的阴离子弗伦克尔无序密度，而阳离子保持有序。因此，淬火随机晶体场和无序交换相互作用可以引入到原本完美的磁性离子烧绿石晶格中。我们表明，无序在低温下防止长程磁序方面可以起到关键作用，相反，会诱导出具有缺陷诱导的冻结磁自由度的强烈涨落的库仑自旋液体。对诸如烧绿石磁性氧化物等受挫自旋系统的实验研究检验了我们对量子多体物理的理解。在此，作者通过实验表明，TbHfO可能是一种用于研究结构无序如何稳定量子自旋液相的模型材料。
