Magnetic anisotropy and reduced neodymium magnetic moments in Nd₃Ru₄Al₁₂

This paper addresses the electronic properties of Nd_3Ru4Al123Ru₄Al₁₂.We performed magnetization measurements on a single crystal in static and pulsed magnetic fields as well as neutron-diffraction experiments. Nd₃Ru₄Al₁₂ is a strongly anisotropic uniaxial ferromagnet with a Curie temperature of 39 K. The magnetic moments are aligned collinearly along the [001] axis. The magnetic structure of Nd₃Ru₄Al₁₂ has orthorhombic symmetry for which the crystallographic Nd site is split into two magnetically inequivalent positions, Nd1 and Nd2. The Nd1 and Nd2 atoms exhibit reduced magnetic moments, 0.95 and 2.66 μ_B, as compared to the free Nd³⁺-ion value (3.28 μ_B). We discuss this finding in terms of crystal-field effects and competing exchange and anisotropy interactions. Since the single-ion mechanism in Nd₃Ru₄Al₁₂ leads to uniaxial anisotropy and the two-ion mechanism of the actinide analog U₃Ru₄Al₁₂ is known to lead to planar anisotropy, this paper demonstrates the decisive influence of these different mechanisms on the magnetic anisotropy.