Magnetic structure and crystal field excitations of NdOs₂Al₁₀: a neutron scattering study

Abstract

We have investigated the magnetic properties of a polycrystalline sample of NdOs2Al10 using neutron diffraction and inelastic neutron scattering, magnetic susceptibility and heat capacity measurements. The magnetic susceptibility data reveal an antiferromagnetic transition at T N1 = 2.2 K while the heat capacity data which extend to lower temperatures show a further transition at T N2 = 1.1 K. The INS measurements detect four well-resolved crystal field excitations at 7.4, 12.4, 17.6 meV and 19.2 meV at 5 K. The positions and intensities of the observed CEF excitations and the temperature dependence of previously published single crystal susceptibility data are analysed based on the orthorhombic CEF model of the J = 9/2 ground state multiplet of Nd3+ ion. The neutron diffraction study reveals the magnetic structure at T = 1.6 K to be of sine wave type (κ = [0, 0.723, 0]) with an ordered state moment of μ Nd 3+ = 1.59(1) μ B aligned along the a-axis in agreement with the single ion crystal field anisotropy. This indicates that the magnetism of NdOs2Al10 is governed by the RKKY interactions in agreement with other RT 2Al10 (R = Nd, Sm, Tb, T = Fe, Ru and Os), but different to that of R = Ce based compounds where anisotropic two ions interaction as well as Kondo interaction govern the anomalous direction of the ordered state moment.

Crossover from Kondo semiconductor to metallic antiferromagnet with5d-electron doping inCeFe2Al10

“…An optical conductivity measurement on CeOs 2 Al 10 has revealed that a charge-density-wavelike instability which develops along the b axis at temperatures slightly higher than T N induces unconventional AFM ordering [16]. This mechanism contrasts with conventional RKKY dominated ordering as in the case of GdT 2 Al 10 [7,27] and NdOs 2 Al 10 [28]. The orthorhombic crystalline-electric field experienced by the f electrons was also proposed to be an important driver for the strong magnetic anisotropy and the small ordered magnetic moments in CeT 2 Al 10 [2,9,[29][30][31].…”

A crossover from Kondo semiconductor to metallic antiferromagnet with $5d$-electron doping in CeFe$_2$Al$_{10}$

“…An optical conductivity measurement on CeOs 2 Al 10 has revealed that a charge-density-wave like instability which develops along the b axis at temperatures slightly higher than T N induces unconventional AFM ordering [16]. This mechanism contrasts with conventional RKKY dominated ordering as in the case of GdT 2 Al 10 [7,27] and NdOs 2 Al 10 [28]. The orthorhombic crystallineelectric field experienced by the f -electrons was also proposed to be an important driver for the strong magnetic anisotropy and the small ordered magnetic moments in CeT 2 Al 10 [2,9,[29][30][31].…”