R(Al, Mn)B₄ (R = Gd ~ Lu)化合物の生成と物理的性質

抄録

Crystals of the new solid compounds Tm(Al_1-xMn_x)B₄ (x = 0.002 ~ 0.100) and R(Al_0.995Mn_0.005)B₄ (R = rare earth), were grown from R₂O₃ and crystalline B powders for Al and Mn mixed flux. Mixture of the starting materials was heated up to1773 K in an Ar atmosphere and kept at that temperature for 5 h, then the molten flux solution was slowly cooled down at a rate of 50 K/h. Tm(Al_1-xMn_x)B₄ compounds were obtained as a single phase from the Al_1-xMn_x flux (x = 0.005 ~ 0.100). R(Al_0.995Mn_0.005)B₄ compounds were obtained as in the case of R(Ho, Er, Tm, Yb, Lu). ThB₄-type compounds were formed in the case of R (Gd, Tb, Dy, Ho). The lattice constants of Ho(Al, Mn)B₄ and Lu(Al, Mn)B₄ obtained were in the range of a = 3.475(1), b = 5.932(1), c = 11.465(1) Å and a = 3.434(1), b = 5.895(1), c = 11.391(1) Å. The lattice constants were smaller than those of RAlB₄ by dissolving Mn atom into Al atom. The values of the hardness for R(Al, Mn)B₄ were in the range of 11.9 ~ 13.7 GPa. The magnetic susceptibilities of both Er(Al_0.995Mn_0.005)B₄ and Yb(Al_0.995Mn_0.005)B₄ show antiferromagnetic transitions at 3.5 K and 12 K, respectively.