论文标题
沸石中钾簇的磁矩和铁磁特性的起源
Origin of magnetic moments and ferromagnetic properties of potassium clusters in zeolite A
论文作者
论文摘要
详细研究了在沸石A中排列的K簇。 k簇是在常规的Alpha-cages a沸石A中生成的,该沸石A的加载k金属以每个alpha-cage的k原子的加载密度为$ n $。 $ n $的值从0更改为7.2。众所周知,该系统以$ n> 2 $的形式显示了铁磁性能,其中Curie温度随$ n $升高,峰值约为$ n $ n约3.6 $,并在$ n = 7.2 $时降至0 k。魏斯温度负为$ n> 2 $估计的魏斯·韦斯法律估计。以前已经提出了一个具有1 $ s $,1 $ p $和1 $ d $量子状态的K群集的球形量子孔(SQW)型号,而铁磁性属性被解释为是由于1 $ p $州的$ s $ electrons所致。已经提出了针对铁磁特性的起源的K群集阵列中Mott-unsulator抗铁磁性的旋转模型。但是,SQW模型无法解释Curie温度的$ N $依赖性或Curie常数的依赖性。在本研究中,对光学反射,磁性特性,电子自旋共振和电阻率进行了详细的测量。在低温下清楚地观察到0.7 eV处的光学反射频带,以$ 2 <n <6 $的形式观察到,并分配给毗邻alpha-cages的1 $ p $ state之间的Sigma键入状态。电阻率表示连续$ n $的绝缘状态。我们提出了一个先进的SQW模型,并考虑了Sigma键入,1 $ P $孔状态的轨道正交性以及超晶格结构。我们使用基于相关极性系统的模型来解释观察到的电子特性。我们提出了通过扩展旋转轨道相互作用的Rashba机制,毗邻$ 1p $轨道之间的Dzyaloshinsky-Moriya(DM)相互作用的增强效应。
K clusters arrayed in zeolite A are investigated in detail. K clusters are generated in regular alpha-cages of zeolite A by the loading of guest K metal at a loading density of K atoms per alpha-cage, $n$. The value of $n$ was changed from 0 to 7.2. It is known that this system shows ferromagnetic properties for $n > 2$, where the Curie temperature increases with $n$, has a peak of approx,8 K at $n approx 3.6$, and decreases to 0 K at $n = 7.2$. The negative Weiss temperature is estimated from the Curie-Weiss law for $n > 2$. A spherical quantum-well (SQW) model for the K cluster with 1$s$, 1$p$, and 1$d$ quantum states has previously been proposed, and the ferromagnetic properties were explained as being due to $s$-electrons in 1$p$ states. A spin-cant model of Mott-insulator antiferromagnetism in a K cluster array has been proposed for the origin of the ferromagnetic properties. However, the SQW model cannot explain either the $n$-dependence of the Curie temperature or that of the Curie constant. In the present study, detailed measurements were made of the optical reflection, magnetic properties, electron spin resonance, and electrical resistivities. An optical reflection band at 0.7 eV is clearly observed for $2 < n < 6$ at low temperatures, and is assigned to the excitation of the sigma-bonding state between 1$p$-states in adjoining alpha-cages. The electrical resistivity indicates an insulating state continuously for $n$. We propose an advanced SQW model with consideration for sigma-bonding, the orbital orthogonality of 1$p$-hole states, and also the superlattice structure. We explain the observed electronic properties using this model based on a correlated polaron system. We propose an enhancement effect of the Dzyaloshinsky-Moriya (DM) interaction between adjoining $1p$ orbitals by the extension of the Rashba mechanism of spin-orbit interaction.