Polarized single crystal neutron diffraction study of the zero-magnetization ferromagnetSm1−xGdxAl2 (x=0.024)<

Field-induced magnetic charge in a cubic Laves compound UAl2

“…Our arguments for the cubic Laves compound are informed by magnetic symmetry, and encompass a successful account of spatial anisotropy in the uranium wavefunction observed in 12 basis-allowed reflections [5]. Similar arguments have been successfully employed to infer the contribution of anapoles to Bragg diffraction patterns of SmAl 2 lightly doped with Gd [23], which is a ferromagnet below a temperature ≈ 127 K [4].…”

“…When the magnetic field is applied along the [1, 1, 1] crystal axis of UAl 2 the diffraction pattern will be different from the one with magnetization induced along [1, 1, 0] discussed in the main text. SmAl 2 actually develops spontaneous ferromagnetism below a critical temperature ≈ 127 K with [1, 1, 1] the easy-axis [4]. The appropriate magnetic spacegroup for magnetization parallel to [1, 1, 1] is R3 m′ (#166.101, magnetic crystal-class 3 m′, D 3d (S 6 )) in which U (or Sm) ions are in sites with symmetry 3m′., namely, 6c at an origin (0, 0, 7/8).…”

“…The neutron polarization technique (flipping ratio) employed by the authors gives access to the real part of the component of 〈Q ⊥ 〉 parallel to the applied magnetic field [4,9], and this component equates to 〈Q ⊥,ξ 〉 with our principal-axes (ξ, η, ζ) in Figure 1. Experimental results are presented as a form factor for the uranium ion that we denote by f(h, k, l).…”

“…Compounds with the C15 cubic Laves structure possess a similar class of forbidden reflections. Specifically, the rare earth and actinide compounds SmAl 2 [4] and UAl 2 [5] display reflections indexed by H o + K o + L o = 4n + 2 that are nominally due to Al nuclei or Al electron distributions alone. The same condition applies to Bragg diffraction when the Laves structure possesses ferromagnetic order, either induced by an applied magnetic field or a spontaneous development below a phase transition.…”

Role of local short-scale correlations in the mechanism of negative magnetization

“…Temperature dependent neutron diffraction data were collected from two axis diffractometer at D4 (Disordered materials diffractometer) in ILL, Grenoble using the wavelength of 0.4994 Å obtained by reflection of a Cu(220) monochromator [31]. Although, the idea of utilizing 'hot neutrons' is remarkable for Gd containing single crystals [32][33][34], but so far any report based on powdered sample is not available in literature. The high counting rate and low background of the D4 instrument [35] have enabled us to unambiguously determine the thermal evolution of magnetic structure.…”