1] Pulsed Field Facility, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA [2] Department of Physics, University of Texas, Austin, Texas 78712, USA.
1] Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [2] Department of Physics, University of California, Berkeley, California 94720, USA.
Nat Commun. 2014 Jun 27;5:4203. doi: 10.1038/ncomms5203.
Spin and orbital quantum numbers play a key role in the physics of Mott insulators, but in most systems they are connected only indirectly--via the Pauli exclusion principle and the Coulomb interaction. Iridium-based oxides (iridates) introduce strong spin-orbit coupling directly, such that these numbers become entwined together and the Mott physics attains a strong orbital character. In the layered honeycomb iridates this is thought to generate highly spin-anisotropic magnetic interactions, coupling the spin to a given spatial direction of exchange and leading to strongly frustrated magnetism. Here we report a new iridate structure that has the same local connectivity as the layered honeycomb and exhibits striking evidence for highly spin-anisotropic exchange. The basic structural units of this material suggest that a new family of three-dimensional structures could exist, the 'harmonic honeycomb' iridates, of which the present compound is the first example.
自旋和轨道量子数在莫特绝缘体的物理学中起着关键作用，但在大多数系统中，它们只是通过泡利不相容原理和库仑相互作用间接关联。基于铱的氧化物（铱酸盐）直接引入强自旋轨道耦合，使得这些数字交织在一起，莫特物理呈现出强烈的轨道特征。在层状的蜂窝状铱酸盐中，这被认为会产生高度各向异性的自旋磁相互作用，将自旋耦合到给定的交换空间方向，并导致强烈的受挫磁性。在这里，我们报告了一种新的铱酸盐结构，它具有与层状蜂窝状相同的局部连接，并表现出强烈的各向异性交换的明显证据。这种材料的基本结构单元表明，可能存在一个新的三维结构家族，即“调和蜂窝状”铱酸盐，本化合物就是其第一个例子。
