Spin freezing in icosahedral Tb-Mg-Zn and Tb-Mg-Cd quasicrystals
Spin freezing in icosahedral Tb-Mg-Zn and Tb-Mg-Cd quasicrystals
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DOI：
10.1088/0953-8984/15/46/014
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发表时间：
2003-11-26
影响因子：
2.7
通讯作者：
Tsai, AP
中科院分区：
文献类型：
--
作者：
Dolinsek, J;Jaglicic, Z;Tsai, AP
用剩余直流磁化强度(TRM)随时效时间和磁场的衰减研究了几何受阻二十面体准晶Tb-Mg-Zn和Tb-Mg-Cd的自旋冻结性质。在低温下，磁化强度表现出典型的破裂遍历现象，这是自旋玻璃(SGS)的特征。然而，在低场区观测到的TRM对磁场的线性依赖与超对称组织自由能中非遍历系统的老化不相容，但与阻塞温度以下超顺磁体的单一整体最小自由能相容。从这个角度来看，Tb-Mg-Zn(Cd)准晶不同于格位无序的SGS，但类似于几何受挫的纯(格位有序)系统，如Kagome和焦绿石反铁磁体，它们在自旋冻结温度以下的磁化和自旋聚集中也表现出超顺磁性成分。Tb-Mg-Zn(Cd)准晶显示出与格位无序SGS和超顺磁性相关联的特征。这种二元性不是准周期结构中自旋的具体特征，但在非随机(按位置排序)几何受阻的磁系统中很常见。
The nature of spin freezing in geometrically frustrated icosahedral quasicrystals Tb-Mg-Zn and Tb-Mg-Cd was studied by thermoremanent dc magnetization (TRM) decay as a function of aging time and magnetic field. At low temperatures the magnetization exhibits typical broken-ergodicity phenomena, as characteristic of spin glasses (SGs). However, the observed linear dependence of the TRM on the magnetic field in the low-field regime is incompatible with the aging of a nonergodic system in an ultrametrically organized free energy of a SG, but compatible with a single-global minimum free energy of a superparamagnet below the blocking temperature. The Tb-Mg-Zn(Cd) quasicrystals are, from this point of view, different from site-disordered SGs, but similar to geometrically frustrated pure (site-ordered) systems, like the kagome and pyrochlore antiferromagnets, which also exhibit a superparamagnetic component in the magnetization below the spin freezing temperature and clustering of spins. The Tb-Mg-Zn(Cd) quasicrystals show features associated with both the site-disordered SGs and the superparamagnets. This duality is not a specific feature of spins in a quasiperiodic structure, but is found quite commonly in nonrandom (site-ordered) geometrically frustrated magnetic systems.