Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA.
J Phys Condens Matter. 2010 Feb 17;22(6):066001. doi: 10.1088/0953-8984/22/6/066001. Epub 2010 Jan 27.
Single crystals of Ln(Cu,Al)12 and Ln(Cu,Ga)12 compounds (Ln = Y, Ce-Nd, Sm, Gd-Ho, and Yb for Al and Ln = Y, Gd-Er, Yb for Ga) have been grown by flux-growth methods and characterized by means of single-crystal x-ray diffraction, complemented with microprobe analysis, magnetic susceptibility, resistivity and heat capacity measurements. Ln(Cu,Ga)12 and Ln(Cu,Al)12 of the ThMn12 structure type crystallize in the tetragonal I4/mmm space group with lattice parameters a approximately 8.59 Å and c approximately 5.15 Å and a approximately 8.75 Å and c approximately 5.13 Å for Ga and Al containing compounds, respectively. For aluminium containing compounds, magnetic susceptibility data show Curie-Weiss paramagnetism in the Ce and Pr analogues down to 50 K with no magnetic ordering down to 3 K, whereas the Yb analogue shows a temperature-independent Pauli paramagnetism. Sm(Cu,Al)12 orders antiferromagnetically at T(N)approximately 5 K and interestingly exhibits Curie-Weiss behaviour down to 10 K with no Van Vleck contribution to the susceptibility. Specific heat data show that Ce(Cu,Al)12 is a heavy fermion antiferromagnet with T(N) approximately 2 K and with an electronic specific heat coefficient γ0 as large as 390 mJ K2 mol(-1). In addition, this is the first report of Pr(Cu,Al)12 and Sm(Cu,Al)12 showing an enhanced mass (approximately 80 and 120 mJ K(2) mol(-1)). For Ga containing analogues, magnetic susceptibility data also show the expected Curie-Weiss behaviour from Gd to Er, with the Yb analogue being once again a Pauli paramagnet. The antiferromagnetic transition temperatures range over 12.5, 13.5, 6.7, and 3.4 K for Gd, Tb, Dy, and Er. Metallic behaviour is observed down to 3 K for all Ga and Al analogues. A large positive magnetoresistance up to 150% at 9 T is also observed for Dy(Cu,Ga)12. The structure, magnetic, and transport properties of these compounds will be discussed.
已通过熔剂生长法生长出 Ln(Cu,Al)12 和 Ln(Cu,Ga)12 化合物（Ln = Y、Ce-Nd、Sm、Gd-Ho 和 Yb 用于 Al 和 Ln = Y、Gd-Er、Yb 用于 Ga）的单晶，并通过单晶 X 射线衍射、微探针分析、磁化率、电阻率和热容测量进行了表征。ThMn12 结构类型的 Ln(Cu,Ga)12 和 Ln(Cu,Al)12 分别在四方 I4/mmm 空间群中结晶，晶格参数 a 约为 8.59 Å，c 约为 5.15 Å，a 约为 8.75 Å，c 约为 5.13 Å 对于含 Ga 和 Al 的化合物。对于含铝化合物，磁化率数据表明 Ce 和 Pr 类似物在 50 K 以下表现出居里-外斯顺磁行为，在 3 K 以下没有磁有序，而 Yb 类似物表现出温度无关的泡利顺磁行为。Sm(Cu,Al)12 在 T(N)约 5 K 下呈反铁磁有序，有趣的是在 10 K 以下表现出居里-外斯行为，磁化率没有范弗莱克贡献。热容数据表明 Ce(Cu,Al)12 是一种重费米子反铁磁体，T(N)约为 2 K，电子热容系数γ0 高达 390 mJ K2 mol(-1)。此外，这是首次报道 Pr(Cu,Al)12 和 Sm(Cu,Al)12 表现出增强的质量（约 80 和 120 mJ K(2) mol(-1)）。对于含 Ga 的类似物，磁化率数据也显示出从 Gd 到 Er 的预期居里-外斯行为，而 Yb 类似物再次表现为泡利顺磁体。反铁磁转变温度范围为 12.5、13.5、6.7 和 3.4 K，分别对应于 Gd、Tb、Dy 和 Er。所有 Ga 和 Al 类似物在 3 K 以下均表现出金属行为。Dy(Cu,Ga)12 还表现出高达 9 T 时 150%的大正磁电阻。将讨论这些化合物的结构、磁性和输运性质。
