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Single-ion magnetism in the extended solid-state: insights from X-ray absorption and emission spectroscopy
Chemical Science ( IF 7.6 ) Pub Date : 2020-10-07 , DOI: 10.1039/d0sc03787g Myron S. Huzan 1, 2, 3, 4, 5 , Manuel Fix 6, 7, 8, 9, 10 , Matteo Aramini 2, 3, 11, 12 , Peter Bencok 2, 3, 11, 12 , J. Frederick W. Mosselmans 2, 3, 11, 12 , Shusaku Hayama 2, 3, 11, 12 , Franziska A. Breitner 6, 7, 8, 9, 10 , Leland B. Gee 4, 13, 14, 15 , Charles J. Titus 13, 14, 15, 16 , Marie-Anne Arrio 17, 18, 19, 20, 21 , Anton Jesche 6, 7, 8, 9, 10 , Michael L. Baker 1, 2, 3, 4, 5
Chemical Science ( IF 7.6 ) Pub Date : 2020-10-07 , DOI: 10.1039/d0sc03787g Myron S. Huzan 1, 2, 3, 4, 5 , Manuel Fix 6, 7, 8, 9, 10 , Matteo Aramini 2, 3, 11, 12 , Peter Bencok 2, 3, 11, 12 , J. Frederick W. Mosselmans 2, 3, 11, 12 , Shusaku Hayama 2, 3, 11, 12 , Franziska A. Breitner 6, 7, 8, 9, 10 , Leland B. Gee 4, 13, 14, 15 , Charles J. Titus 13, 14, 15, 16 , Marie-Anne Arrio 17, 18, 19, 20, 21 , Anton Jesche 6, 7, 8, 9, 10 , Michael L. Baker 1, 2, 3, 4, 5
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Large single-ion magnetic anisotropy is observed in lithium nitride doped with iron. The iron sites are two-coordinate, putting iron doped lithium nitride amongst a growing number of two coordinate transition metal single-ion magnets (SIMs). Uniquely, the relaxation times to magnetisation reversal are over two orders of magnitude longer in iron doped lithium nitride than other 3d-metal SIMs, and comparable with high-performance lanthanide-based SIMs. To understand the origin of these enhanced magnetic properties a detailed characterisation of electronic structure is presented. Access to dopant electronic structure calls for atomic specific techniques, hence a combination of detailed single-crystal X-ray absorption and emission spectroscopies are applied. Together K-edge, L2,3-edge and Kβ X-ray spectroscopies probe local geometry and electronic structure, identifying iron doped lithium nitride to be a prototype, solid-state SIM, clean of stoichiometric vacancies where Fe lattice sites are geometrically equivalent. Extended X-ray absorption fine structure and angular dependent single-crystal X-ray absorption near edge spectroscopy measurements determine FeI dopant ions to be linearly coordinated, occupying a D6h symmetry pocket. The dopant engages in strong 3dπ-bonding, resulting in an exceptionally short Fe–N bond length (1.873(7) Å) and rigorous linearity. It is proposed that this structure protects dopant sites from Renner–Teller vibronic coupling and pseudo Jahn–Teller distortions, enhancing magnetic properties with respect to molecular-based linear complexes. The Fe ligand field is quantified by L2,3-edge XAS from which the energy reduction of 3dz2 due to strong 4s mixing is deduced. Quantification of magnetic anisotropy barriers in low concentration dopant sites is inhibited by many established methods, including far-infrared and neutron scattering. We deduce variable temperature L3-edge XAS can be applied to quantify the J = 7/2 magnetic anisotropy barrier, 34.80 meV (∼280 cm−1), that corresponds with Orbach relaxation via the first excited, MJ = ±5/2 doublet. The results demonstrate that dopant sites within solid-state host lattices could offer a viable alternative to rare-earth bulk magnets and high-performance SIMs, where the host matrix can be tailored to impose high symmetry and control lattice induced relaxation effects.
中文翻译：
扩展固态中的单离子磁性：X射线吸收和发射光谱学的见解
在掺杂铁的氮化锂中观察到较大的单离子磁各向异性。铁的位置是两个坐标的，这使得掺杂铁的氮化锂成为越来越多的两个坐标过渡金属单离子磁体（SIM）的一部分。独特的是，掺铁的氮化锂中的磁化反转弛豫时间比其他3d金属SIMs长两个数量级以上，并且与基于镧系元素的高性能SIMs相当。为了理解这些增强的磁性的起源，提出了电子结构的详细表征。进入掺杂剂电子结构需要特定于原子的技术，因此将详细的单晶X射线吸收光谱和发射光谱结合起来使用。一起K-edge，L 2,3边和KβX射线光谱仪探测局部几何形状和电子结构，确定掺铁的氮化锂为原型固态SIM，清除了化学计量空位，其中Fe晶格位在几何上是等效的。扩展的X射线吸收精细结构和与角度相关的单晶X射线吸收近边缘光谱测量确定了Fe I掺杂离子是线性配位的，占据D 6h对称的口袋。掺杂剂参与强3dπ键合，从而导致Fe-N键长极短（1.873（7）Å）和严格的线性。有人提出，这种结构可以保护掺杂剂位点免受Renner-Teller振动耦合和拟Jahn-Teller变形的影响，从而增强基于分子的线性络合物的磁性。Fe配体场通过L 2,3 -edge XAS定量，由此推断由于强4s混合而导致的3d z 2能量减少。低浓度掺杂剂位点中的磁各向异性势垒的量化受到许多已建立方法的抑制，包括远红外和中子散射。我们推论出温度可变的L 3 -edge XAS可用于量化J= 7/2磁各向异性势垒，34.80 meV（〜280 cm -1），对应于通过第一次激发的Orbach弛豫，M J =±5/2 doublet。结果表明，固态基质晶格中的掺杂剂位点可以为稀土体磁体和高性能SIM提供可行的替代方案，其中基质基质可以定制为施加高对称性并控制晶格诱导的弛豫效果。
更新日期：2020-10-12
中文翻译：
扩展固态中的单离子磁性：X射线吸收和发射光谱学的见解
在掺杂铁的氮化锂中观察到较大的单离子磁各向异性。铁的位置是两个坐标的，这使得掺杂铁的氮化锂成为越来越多的两个坐标过渡金属单离子磁体（SIM）的一部分。独特的是，掺铁的氮化锂中的磁化反转弛豫时间比其他3d金属SIMs长两个数量级以上，并且与基于镧系元素的高性能SIMs相当。为了理解这些增强的磁性的起源，提出了电子结构的详细表征。进入掺杂剂电子结构需要特定于原子的技术，因此将详细的单晶X射线吸收光谱和发射光谱结合起来使用。一起K-edge，L 2,3边和KβX射线光谱仪探测局部几何形状和电子结构，确定掺铁的氮化锂为原型固态SIM，清除了化学计量空位，其中Fe晶格位在几何上是等效的。扩展的X射线吸收精细结构和与角度相关的单晶X射线吸收近边缘光谱测量确定了Fe I掺杂离子是线性配位的，占据D 6h对称的口袋。掺杂剂参与强3dπ键合，从而导致Fe-N键长极短（1.873（7）Å）和严格的线性。有人提出，这种结构可以保护掺杂剂位点免受Renner-Teller振动耦合和拟Jahn-Teller变形的影响，从而增强基于分子的线性络合物的磁性。Fe配体场通过L 2,3 -edge XAS定量，由此推断由于强4s混合而导致的3d z 2能量减少。低浓度掺杂剂位点中的磁各向异性势垒的量化受到许多已建立方法的抑制，包括远红外和中子散射。我们推论出温度可变的L 3 -edge XAS可用于量化J= 7/2磁各向异性势垒，34.80 meV（〜280 cm -1），对应于通过第一次激发的Orbach弛豫，M J =±5/2 doublet。结果表明，固态基质晶格中的掺杂剂位点可以为稀土体磁体和高性能SIM提供可行的替代方案，其中基质基质可以定制为施加高对称性并控制晶格诱导的弛豫效果。
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