Institut Laue-Langevin, Boite Postale 156, F-38042 Grenoble, France.
J Phys Condens Matter. 2010 May 26;22(20):206002. doi: 10.1088/0953-8984/22/20/206002. Epub 2010 Apr 26.
Neutron diffraction, susceptibility and magnetization measurements (for R = Er only) were performed on iron borates RFe(3)(BO(3))(4) (R = Pr, Er) to investigate details of the crystallographic structure, the low temperature magnetic structures and transitions and to study the role of the rare earth anisotropy. PrFe(3)(BO(3))(4), which crystallizes in the spacegroup R32, becomes antiferromagnetic at T(N) = 32 K, with τ = [0 0 3/2], while ErFe(3)(BO(3))(4), which keeps the P3(1)21 symmetry over the whole studied temperature range 1.5 K < T < 520 K, becomes antiferromagnetic below T(N) = 40 K, with τ = [0 0 1/2]. Both magnetic propagation vectors lead to a doubling of the crystallographic unit cell in the c-direction. Due to the strong polarization of the Fe-sublattice, the magnetic ordering of the rare earth sublattices appears simultaneously at T(N). The moment directions are determined by the rare earth anisotropy: easy-axis along c for PrFe(3)(BO(3))(4) and easy-plane a-b for ErFe(3)(BO(3))(4). There are no spin reorientations present in either of the two compounds but there is the appearance below 10 K of a minority phase in the Er-compound adopting a 120° arrangement of the Er-moments.
对铁硼酸盐 RFe(3)(BO(3))(4)（R = Pr，Er）进行了中子衍射、磁化率和磁化强度测量（仅对 Er 进行），以研究晶体结构、低温磁结构和转变的细节，并研究稀土各向异性的作用。PrFe(3)(BO(3))(4)在 R32 空间群中结晶，在 T(N) = 32 K 时变为反铁磁体，τ = [0 0 3/2]，而 ErFe(3)(BO(3))(4)在整个研究温度范围内保持 P3(1)21 对称性 1.5 K < T < 520 K，在 T(N) = 40 K 以下变为反铁磁体，τ = [0 0 1/2]。这两个磁传播矢量导致晶体单元在 c 方向上加倍。由于 Fe 亚晶格的强烈极化，稀土亚晶格的磁序在 T(N)处同时出现。磁矩方向由稀土各向异性决定：对于 PrFe(3)(BO(3))(4)，沿 c 轴为易轴，对于 ErFe(3)(BO(3))(4)，沿 a-b 轴为易面。在这两种化合物中都没有自旋重定向，但在 Er 化合物中，在 10 K 以下会出现一种少数相，其 Er 磁矩呈 120°排列。
