Ultrafast relaxation rates and reversal time in disordered ferrimagnets
Ultrafast relaxation rates and reversal time in disordered ferrimagnets
复制标题
无序亚铁磁体中的超快弛豫率和反转时间
DOI：
--
复制
发表时间：
2015
期刊：
影响因子：
--
通讯作者：
O. Chubykalo
中科院分区：
文献类型：
--
作者：
O. Suarez;P. Nieves;D. Laroze;D. Altbir;O. Chubykalo
在对超快激光脉冲的响应中，单相金属被分为“快”（在100 fs量级的时间尺度上磁化猝灭，在几皮秒及以下的时间尺度上恢复）和“慢”（具有更长的特征时间尺度）。由“快”跃迁（TM）和“慢”稀土金属（RE）组合而成的无序铁磁性合金表现出由热机制介导的超快全光开关。偶联合金的特征时间尺度行为更为复杂，受亚晶格间交换、掺杂（RE）浓度和温度等诸多参数的影响。这里，在Landau-Lifshitz-Bloch框架内分析了每个子格的纵向松弛时间。我们表明，对于中等的亚晶格间耦合强度，两种材料作为慢速（RE）材料浓度的函数减慢。对于较大的耦合，快（TM）材料可能变得更快，而慢（RE）材料仍然更慢。这些结论可能对部分聚类的无序铁磁体（如GdFeCo）的开关时间有重要意义。利用原子模型，我们发现在中等耦合情况下，反转会从富钆区开始，而在耦合强度较大的情况下，反转可能会发生。
In response to ultrafast laser pulses, single-phase metals have been classified as “fast” (with magnetization quenching on the time scale of the order of 100 fs and recovery in the time scale of several picoseconds and below) and “slow” (with longer characteristic time scales). Disordered ferrimagnetic alloys consisting of a combination of “fast” transition (TM) and “slow” rare-earth (RE) metals have been shown to exhibit an ultrafast all-optical switching mediated by the heat mechanism. The behavior of the characteristic time scales of coupled alloys is more complicated and is influenced by many parameters such as the intersublattice exchange, doping (RE) concentration, and the temperature. Here, the longitudinal relaxation times of each sublattice are analyzed within the Landau-Lifshitz-Bloch framework. We show that for moderate intersublattice coupling strength both materials slow down as a function of slow (RE) material concentration. For larger coupling, the fast (TM) material may become faster, while the slow (RE) one is still slower. These conclusions may have important implications in the switching time of disordered ferrimagnets such as GdFeCo with partial clustering. Using atomistic modeling, we show that in the moderately coupled case, the reversal would start in the Gd-rich region, while the situation may be reversed if the coupling strength is larger.