CoMOF5(pyrazine)(H2O)(2)(M = Nb, Ta): Two-Layered Cobalt Oxyfluoride Antiferromagnets with Spin Flop Transitions
CoMOF5(pyrazine)(H2O)(2)(M = Nb, Ta): Two-Layered Cobalt Oxyfluoride Antiferromagnets with Spin Flop Transitions
复制标题
CoMOF5(pyrazine)(H2O)(2)(M = Nb, Ta)：具有自旋翻转跃迁的两层氟氧化钴反铁磁体
DOI：
10.1021/acs.inorgchem.1c01654
复制
发表时间：
2021
影响因子：
4.6
通讯作者：
Lu Hongcheng
中科院分区：
文献类型：
--
作者：
Zhou Yadong;Wang Yanhong;Cao Jiaojiao;Zeng Zhuo;Zhou Taiping;Liao Rongzhen;Wang Tao;Wang Zhenxing;Xia Zhengcai;Ouyang Zhongwen;Lu Hongcheng
采用传统的水热法合成了两种氟氧化钴反铁磁体CoMOF 5（pyz）（H2O）2（M = Nb 1，Ta 2; pyz =吡嗪），并通过热重分析、红外光谱、电子自旋共振（ESR）、静态低场和脉冲高场磁化率和磁化强度的测量对其进行了表征. X射线单晶衍射分析表明，化合物1和2均为同构晶体，空间群为C2/m，二维Co 2+三角晶格在ab平面内，沿轴向被沿着排列的CoMOF 5（M = Nb 1，Ta 2）八面体隔开，三角晶格间Co···Co间距较大。由于化合物1和2的低维性和受抑三角晶格，在13.7 K之前，化合物1和2没有表现出长程反铁磁有序。此外，自旋翻转转变观察到的磁化曲线在2 K的两个化合物，这是进一步证实了ESR谱。此外，ESR谱表明在两种化合物中存在零场自旋能隙。在2K下测量的高场磁化强度在107 T处饱和，在减去货车Vleck顺磁贡献之后，Ms分别为1.55 μ B（对于1）和1.71 μ B（对于2），这通常在低温下对于赝自旋为1/2的Co 2+离子观察到。粉末平均磁各向异性g = 3.10（1）（3.42（2））和磁超交换相互作用J/kB=-3.2 K（1）（-3.6 K（2））。
Two cobalt oxyfluoride antiferromagnets CoMOF5(pyz)(H2O)2(M = Nb1, Ta2; pyz = pyrazine) have been synthesized via conventional hydrothermal methods and characterized by thermogravimetric (TGA) analysis, FTIR spectroscopy, electron spin resonance (ESR), magnetic susceptibility, and magnetization measurements at both static low field and pulsed high field. The single-crystal X-ray diffraction indicates both compounds1and2are isostructural and crystallize in the monoclinic space groupC2/mwith a two-dimensional Co2+triangular lattice in theabplane, separated by the nonmagnetic MOF5(M = Nb1, Ta2) octahedra along thec-axis with large intertriangular-lattice Co···Co distance. Because of low dimensionality together with frustrated triangular lattice, compounds1and2exhibit no long-range antiferromagnetic order until ∼3.7 K. Moreover, a spin flop transition is observed in the magnetization curves at 2 K for both compounds, which is further confirmed by ESR spectra. In addition, the ESR spectra suggest the presence of a zero-field spin gap in both compounds. The high field magnetization measured at 2 K saturates at ∼7 T withMs= 1.55 μBfor1and 1.71 μBfor2, respectively, after subtracting the Van Vleck paramagnetic contribution, which is usually observed for Co2+ions with pseudospin spin of 1/2 at low temperature. Powder-averaged magnetic anisotropy ofg= 3.10 for1(3.42 for2) and magnetic superexchange interactionJ/kB= −3.2 K for1(−3.6 K for2) are obtained.