Slow dynamics in the geometrically frustrated magnet ZnFe2O4: Universal features of aging phenomena in spin glasses
Slow dynamics in the geometrically frustrated magnet ZnFe2O4: Universal features of aging phenomena in spin glasses
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DOI：
10.1103/physrevb.90.014440
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发表时间：
2014-07-31
影响因子：
3.7
通讯作者：
Ishigaki, T.
中科院分区：
文献类型：
--
作者：
Mamiya, H.;Tsujii, N.;Ishigaki, T.
为了阐明自旋玻璃的普遍特征，我们使用时间分辨中子衍射和磁力测量，仔细研究了几何受挫磁体 ZnFe2O4 中的慢动力学，该磁体具有轻微的紊乱，被视为“非常规”海森堡自旋玻璃。结果表明，“老化”不能归因于漫散射检测到的短程有序的增长，而是归因于隐藏的非周期性相关性的老化，正如自旋玻璃理论所预期的那样。关于衰老，发现了奇怪的行为；如果在等温缓慢弛豫过程中短暂加热/冷却样品，则热剩磁的衰减会极度加速。相反，当短暂加热/冷却后温度恢复时，尽管不存在磁场，磁化强度仍令人惊讶地增加。该行为可以解释为由于热扰动导致老化自旋构型的不稳定以及随后在不稳定后原始自旋构型的自发恢复。虽然在固定能量景观中冻结成许多亚稳态期间不会发生这种不稳定和恢复，但在具有温度敏感漏斗状结构的能量景观中，这些是可能的。这些特征与液滴图片的鬼域场景一致，与稀磁合金和稀磁半导体等传统海森堡自旋玻璃相同。换句话说，它们是海森堡自旋玻璃的普遍特征，包括非常规的特征。
To clarify the universal features of spin glasses, we carefully studied slow dynamics in a geometrically frustrated magnet ZnFe2O4 with slight disorders, regarded as an "unconventional" Heisenberg spin glass, using time-resolved neutron diffractometry and magnetometry. The results indicate that "aging" can be attributed not to growth of the short-range order detected by a diffuse scattering but to aging of a hidden aperiodic correlation, as expected from theories for spin glasses. Concerning aging, peculiar behavior was found; the decay of thermoremanent magnetization is extremely accelerated if the sample is heated/cooled briefly midway through the isothermal slow relaxation. Conversely, magnetization surprisingly increases despite the absence of a magnetic field when the temperature returns after the brief heating/cooling. The behavior can be explained as a destabilization of the aged spin configuration due to the thermal perturbations and subsequent spontaneous restoration of the original spin configuration after the destabilization. Whereas such destabilization and restoration do not occur during freezing into numerous metastable states in a fixed energy landscape, these are possible in an energy landscape with a temperature-sensitive funnel-like structure. These features, consistent with the ghost domain scenario of the droplet picture, are the same as for conventional Heisenberg spin glasses such as dilute magnetic alloys and dilute magnetic semiconductors. In other words, they are universal features in Heisenberg spin glasses including unconventional ones.