Evidence for two distinct spin relaxation mechanisms in 'hot' spin ice Ho2Ti2O7
Evidence for two distinct spin relaxation mechanisms in 'hot' spin ice Ho2Ti2O7
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DOI：
10.1088/0953-8984/16/11/010
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发表时间：
2004-03-24
影响因子：
2.7
通讯作者：
Gardner, JS
中科院分区：
文献类型：
--
作者：
Ehlers, G;Cornelius, AL;Gardner, JS
利用中子散射和交流磁化率技术研究了自旋冰材料Ho_2Ti_2O_7在热顺磁相（T > 1K）的自旋弛豫过程。中子自旋回波（NSE）证明，高于T类似或等于15 K的自旋动力学是由热激活的单离子过程。在较低的温度下（T < 15 K），这不能解释交流磁化率测量中发现的自旋动力学。据推断，第二个较慢的过程，具有不同的热特征占主导地位。我们认为，这是一个量子力学隧穿过程之间的不同的自旋状态分开的一个大的能量障碍。
Neutron scattering and ac-susceptibility techniques have been performed on the spin ice material Ho2Ti2O7 to study the spin relaxation processes in the 'hot' paramagnetic phase (T > 1 K). Neutron spin echo (NSE) proves that above T similar or equal to 15 K the spin dynamics are governed by a thermally activated single-ion process. At lower temperatures (T < 15 K) this cannot account for the spin dynamics found in ac-susceptibility measurements. It is inferred that a second, slower process, with a different thermal signature dominates. We suggest that this is a quantum-mechanical tunnelling process between different spin states separated by a large energy barrier.