Kinetically inhibited order in a diamond-lattice antiferromagnet
Kinetically inhibited order in a diamond-lattice antiferromagnet
复制标题
金刚石晶格反铁磁体中的动力学抑制顺序
DOI：
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发表时间：
2011
影响因子：
11.1
通讯作者：
S. Nagler
中科院分区：
文献类型：
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作者：
G. MacDougall;D. Gout;J. Zarestky;G. Ehlers;A. Podlesnyak;M. McGuire;D. Mandrus;S. Nagler
受抑磁系统表现出高度简并的基态和强烈的涨落，往往导致新的物理。当前感兴趣的一个有趣的例子是金刚石晶格上的反铁磁体，在A位尖晶石材料中物理实现。这是一个三维的原型系统，其中的挫折来自相互竞争的相互作用，而不是纯粹的几何约束，理论表明在低温下不寻常的磁序的可能性。在这里，我们提出了一个全面的单晶中子散射研究CoAl 2 O 4，一个高度受挫的A-网站尖晶石。我们观察到强烈的漫散射，峰值波矢量与Néel有序。低于温度T_∞ = 6.5 K时，伴随着定义明确的自旋波激发的出现，弹性散射线形发生了巨大的变化。以前人们认为，玻璃态行为的发生与玻璃态的出现有关。我们的新结果表明，相反，T ε表示一级相变，但真正的长程有序抑制域壁的动力学冻结。这种情况可能会广泛地发生在包含一级相变的受挫折系统中，并且是对其他材料中异常玻璃化行为的现有报告的自然解释。
Frustrated magnetic systems exhibit highly degenerate ground states and strong fluctuations, often leading to new physics. An intriguing example of current interest is the antiferromagnet on a diamond lattice, realized physically in A-site spinel materials. This is a prototypical system in three dimensions where frustration arises from competing interactions rather than purely geometric constraints, and theory suggests the possibility of unusual magnetic order at low temperature. Here, we present a comprehensive single-crystal neutron scattering study of CoAl2O4, a highly frustrated A-site spinel. We observe strong diffuse scattering that peaks at wavevectors associated with Néel ordering. Below the temperature T∗ = 6.5 K, there is a dramatic change in the elastic scattering lineshape accompanied by the emergence of well-defined spin-wave excitations. T∗ had previously been associated with the onset of glassy behavior. Our new results suggest instead that T∗ signifies a first-order phase transition, but with true long-range order inhibited by the kinetic freezing of domain walls. This scenario might be expected to occur widely in frustrated systems containing first-order phase transitions and is a natural explanation for existing reports of anomalous glassy behavior in other materials.