Neutron Diffraction Study on Intermetallic Er{sub}5Mg{sub}24 and Tm{sub}5Mg{sub}24

摘要

Neutron powder diffraction on the binary intermetallics Er{sub}5Mg{sub}24 and Tm{sub}5Mg{sub}24 confirms their isostructural and pure crystallization in the Ti{sub}5Re{sub}24-type structure (space group 143m, Z = 2) with rare earths located in 2a(0,0,0) and 8c(x,x,x) and Mg in two different 24g(x,y,x) sites. Room temperature lattice constants are 11.263(2) A and 11.215(1) A for the Er and Tm compound, respectively. Atomic positions have been refined. Both compounds order ferromagnetically below Curie temperatures of 17.5(5) K and 7.5(5) K for Er{sub}5Mg{sub}24 and Tm{sub}5Mg{sub}24, respectively. The magnitudes of the Er moments at 4.2 K are 7.5(2) μ{sub}B and 4.4(2) μ{sub}B on the 2a and the 8c sites, respectively. The Tm moments which have been refined from 2 K measurements amount to 3.0(3) μ{sub}B and 2.8(2) μ{sub}B, respectively. The temperature dependencies of the magnetic Bragg intensities reveal distinct deviations from Brillouin curves for J = 15/2 (Er) and J = 6 (Tm) systems and indicate a complex magnetic exchange.