Crystal structure and physical properties of polymorphs of LnAlB4 (Ln = Yb, Lu)
Crystal structure and physical properties of polymorphs of LnAlB4 (Ln = Yb, Lu)
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DOI：
10.1021/cm062244
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发表时间：
2007-04-17
影响因子：
8.6
通讯作者：
Chan, Julia Y.
中科院分区：
文献类型：
--
作者：
Macaluso, Robin T.;Nakatsuji, Satoru;Chan, Julia Y.
在过量的Al助熔剂中生长了YbAlB_4单晶。发现了板状和针状晶体，发现板状晶体是β-YbAlB_4，它具有ThMoB_4结构类型，空间群为Cmmm（No.65），Z = 4，晶格参数为a = 7.3080（4），B = 9.3150（5），c = 3.4980（2）埃。针状晶体被鉴定为YbAlB 4的第一种形式，其以YCrB 4结构类型结晶，空间群Pbam（No.55），Z = 4，晶格参数a = 5.9220（2），B = 11.4730（3），c = 3.5060（5）埃。虽然这两种化合物都具有重费米子基态，具有类似伊辛的磁各向异性，但电子比热系数（γ）不同。β相的γ值接近300 mJ mol（-1）K-2，是α相γ = 130 mJ mol（-1）K-2的两倍多。两种多晶型的结构和物理性质的比较。
Single crystals of YbAlB4 were grown in excess Al flux. Plate- and needle-shaped crystals were found. The plates are found to be beta-YbAlB4, which crystallizes with the ThMoB4 structure type in space group Cmmm (No. 65), Z = 4, with lattice parameters of a = 7.3080(4), b = 9.3150(5), and c = 3.4980(2) angstrom. The needle-shaped crystals were identified as the first form of YbAlB4 which crystallizes with the YCrB4 structure type in space group Pbam (No. 55), Z = 4, with lattice parameters of a = 5.9220(2), b = 11.4730(3), and c = 3.5060(5) angstrom. While both compounds have heavy fermion ground states with Ising-like magnetic anisotropy, the electronic specific heat coefficients (gamma) differ. The beta-phase has a gamma value near 300 mJ mol(-1) K-2, more than twice that of the alpha-phase, gamma = 130 mJ mol(-1) K-2. A comparison of the structures and physical properties of both polymorphs is presented.