Department of Physics, Royal Holloway, University of London, Egham, TW20 0EX, UK.
Institut Laue-Langevin, CS 20156, 38042, Grenoble Cedex 9, France.
Nat Commun. 2019 Feb 7;10(1):637. doi: 10.1038/s41467-019-08598-z.
Pyrochlore systems are ideally suited to the exploration of geometrical frustration in three dimensions, and their rich phenomenology encompasses topological order and fractional excitations. Classical spin ices provide the first context in which it is possible to control emergent magnetic monopoles, and anisotropic exchange leads to even richer behaviour associated with large quantum fluctuations. Whether the magnetic ground state of YbTiO is a quantum spin liquid or a ferromagnetic phase induced by a Higgs transition appears to be sample dependent. Here we have determined the role of structural defects on the magnetic ground state via the diffuse scattering of neutrons. We find that oxygen vacancies stabilise the spin liquid phase and the stuffing of Ti sites by Yb suppresses it. Samples in which the oxygen vacancies have been eliminated by annealing in oxygen exhibit a transition to a ferromagnetic phase, and this is the true magnetic ground state.
烧绿石体系非常适合探索三维几何各向异性，其丰富的现象学包括拓扑序和分数激发。经典自旋冰为控制新兴磁单极子提供了第一个可能的环境，各向异性交换导致了与大量子涨落相关的更丰富的行为。YbTiO 的磁基态是量子自旋液体还是希格斯相变诱导的铁磁相似乎取决于样品。在这里，我们通过中子的漫散射确定了结构缺陷对磁基态的作用。我们发现氧空位稳定了自旋液体相，而 Yb 填充 Ti 位则抑制了它。通过在氧气中退火消除氧空位的样品表现出铁磁相转变，这才是真正的磁基态。
