We present the crystal structures and magnetic properties of a series of magnetic compounds, MIIN(CN)2}2, where M=Cu (1), Ni (2), Co (3) and Fe (4), and [MnN(CN)2}2(C2H5OH)2]Z·(CH3)2CO (5). In the isostructural compounds 1–4, the dicyanamide anion is triply coordinating through its three nitrogen atoms. It bridges the metal ions to form infinite 3D metal-organic frameworks with a rutile-type structure. The framework contains doubly bridged M(–Nâ–·C–N–Câ–·N–)2 ribbons that link approximately orthogonally through the amide nitrogen atoms. The Jahn–Teller distortion in 1 has a strong influence on the packing arrangement (M–N bond lengths: 1.98 and 2.47 Å for 1 and 2.10 and 2.15 Å for 3). On lowering the temperature the bond distances in 1 remain unchanged except for a decrease of the M–Namide length to 2.45 Å. Magnetic data for 1 obey the Curie–Weiss law (Θ=-2.1 K). 2 and 3 are ferromagnets with Curie temperatures (TC) of 9 and 21 K and are characterized by hysteresis loops of 710 and 7975 Oe at 2 K, remnant magnetization, magnetization approaching the expected saturation (gS) of 2 and 3 µB in high field, absorptive component (χ″) in the AC magnetization and λ peak in the heat capacity data. 4 is similarly characterized and shows behaviour that is characteristic of a canted antiferromagnet: the Weiss constant is temperature dependent (+3 K in the range 200–300 K), there is a sharper peak than for 1 or 2 in the AC magnetization and the isothermal magnetization at 3 K increases monotonically to ≈1.3 µB (expected to be 4 µB for ferromagnetic alignment of the spins) in a field of 8 T. Its coercive field (17800 Oe) is the largest observed for any metal-organic compound and exceeds those of alloys of SmCo5 and Nd2Fe14B. The maximum energy product (B · H) is the highest for 3 and is comparable to alloys of Sm–Co. We attribute the large coercive field to a combination of single ion and particle shape anisotropies. 5 is paramagnetic at high temperature with Θ=-3 K. Below 16 K it behaves as a canted antiferromagnet with a very weak resultant spontaneous magnetization.
我们展示了一系列磁性化合物 MIIN(CN)2}2 的晶体结构和磁性能,其中 M=Cu (1)、Ni (2)、Co (3) 和 Fe (4),以及 [ MnN(CN)2}2(C2H5OH)2]Z·(
CH3)2CO (5)。在同构化合物 1-4 中,二
氰胺阴离子通过其三个氮原子进行三重配位。它桥接
金属离子,形成具有
金红石型结构的无限 3D
金属有机框架。该框架包含双桥联的 M(–N–·C–N–C–·N–)2 带,通过酰胺氮原子近似正交地连接。 1 中的 Jahn-Teller 畸变对堆积排列有很大影响(M-N 键长:1 为 1.98 和 2.47 Å,3 为 2.10 和 2.15 Å)。降低温度时,1 中的键距保持不变,只是 M-Namide 长度减小至 2.45 Å。 1 的磁数据遵循居里-韦斯定律 (θ=-2.1 K)。 2 和 3 是居里温度 (TC) 分别为 9 和 21 K 的
铁磁体,其特征是 2 K 时的磁滞回线为 710 和 7975 Oe,剩余磁化强度、在高场中接近 2 和 3 µB 的预期饱和度 (gS) 的磁化强度、交流磁化中的吸收分量 (χ") 和热容量数据中的 λ 峰值。图 4 具有类似的特征,并显示了倾斜反
铁磁体特征的行为:Weiss 常数与温度相关(在 200–300 K 范围内为 +3 K),在交流磁化中存在比 1 或 2 更尖锐的峰值,并且在 8 T 磁场中,3 K 的等温磁化强度单调增加至 ≈1.3 µB(自旋
铁磁排列预计为 4 µB)。其矫顽场 (17800 Oe) 是所有
金属有机化合物中观察到的最大,超过SmCo5 和 Nd2Fe14B 合
金的那些。最大能积 (B·H) 是 3 中最高的,与 Sm-Co 合
金相当。我们将大矫顽场归因于单个离子和粒子形状各向异性的组合。 5 在高温下呈顺磁性,θ=-3 K。低于 16 K,它表现为倾斜反
铁磁体,产生的自发磁化强度非常弱。