National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047, Japan.
Inorg Chem. 2012 Mar 5;51(5):2860-6. doi: 10.1021/ic202018r. Epub 2012 Feb 16.
Single-crystalline samples of a new Zintl compound, Eu(3)Ga(2)P(4), have been synthesized by a Ga-flux method. Eu(3)Ga(2)P(4) is found to crystallize in a monoclinic unit cell, space group C2/c, isostructural to Ca(3)Al(2)As(4). The structure is composed of a pair of edge-shared GaP(4) tetrahedra, which link by corner-sharing to form Ga(2)P(4) two-dimensional layers, separated by Eu(2+) ions. Magnetic susceptibility showed a Curie-Weiss behavior with an effective magnetic moment consistent with the value for Eu(2+) magnetic ions. Below 15 K, ferromagnetic ordering was observed and the saturation magnetic moment was 6.6 μ(B). Electrical resistivity measurements on a single crystal showed semiconducting behavior. Resistivity in the temperature range between 280 and 300 K was fit by an activation model with an energy gap of 0.552(2) eV. The temperature dependence of the resistivity is better described by the variable-range-hopping model for a three-dimensional conductivity, suggesting that Eu-P bonds are involved in the conductivity. A large magnetoresistance, up to -30%, is observed with a magnetic field H = 2 T at T = 100 K, suggesting strong coupling of carriers with the Eu(2+) magnetic moment.
通过 Ga 通量法合成了一种新的 Zintl 化合物 Eu(3)Ga(2)P(4)的单晶样品。Eu(3)Ga(2)P(4)被发现结晶为单斜晶胞，空间群为 C2/c，与 Ca(3)Al(2)As(4)同构。该结构由一对边缘共享的 GaP(4)四面体组成，这些四面体通过角共享连接形成 Ga(2)P(4)二维层，由 Eu(2+)离子隔开。磁化率表现出居里-外斯行为，有效磁矩与 Eu(2+)磁离子的磁矩一致。在 15 K 以下，观察到铁磁有序，饱和磁矩为 6.6 μ(B)。单晶的电阻率测量显示出半导体行为。在 280 至 300 K 之间的温度范围内，电阻率通过具有 0.552(2) eV 能隙的激活模型拟合。电阻率随温度的变化更适合于三维电导率的变程跳跃模型，表明 Eu-P 键参与了电导率。在 T = 100 K 时，磁场 H = 2 T 下观察到高达 -30%的大磁电阻，表明载流子与 Eu(2+)磁矩的强烈耦合。
