Abstract
We have carried out a careful magnetic neutron scattering study of the heavy fermion compound URu2Si2 to probe the possible existence of a small magnetic moment parallel to tetragonal basal plane in the ‘hidden-order’ phase. This small in-plane component of the magnetic moment on the uranium sites S∥ has been postulated by two recent models (rank-5 superspin/hastatic order) aiming to explain the hidden-order phase, in addition to the well-known out-of-plane component S⊥ ≈ 0.01–0.04 μB/U. In order to separate S∥ and S⊥, we take advantage of the condition that for magnetic neutron scattering only the components of the magnetic structure that are perpendicular to the scattering vector Q contribute to the magnetic scattering. We find no evidence for an in-plane magnetic moment S∥. Based on the statistics of our measurement, we establish that the upper experimental limit for the size of any possible in-plane component is Smax∥ ⩽ 1 × 10−3 μB/U.
Highlights
In compounds that contain transition metal, lanthanide, or actinide ions with partially filled d- or f -electron shells, the strong electronic correlations originating in the hybridization of localized d- or f -electron and conduction electron states often leads to the emergence of new electronic ground states such as heavy fermion metals, complex magnetic order, quadrupolar order, non-Fermi-liquid (NFL) behavior, and unconventional superconductivity (SC) [1]
We note that the absence of a static in-plane component of the magnetic moment S may be explained in terms of a fluctuating in-plane component
We note that because our experiment was carried out in the diffraction mode of BT7 where the intensities are integrated over all final neutron energies after the scattering process at the sample, a fluctuating moment S should have still led to some increased intensity at the [003] reciprocal space position if both the moment and the lifetime of the fluctuations were large enough
Summary
In compounds that contain transition metal, lanthanide, or actinide ions with partially filled d- or f -electron shells, the strong electronic correlations originating in the hybridization of localized d- or f -electron and conduction electron states often leads to the emergence of new electronic ground states such as heavy fermion metals, complex magnetic order, quadrupolar order, non-Fermi-liquid (NFL) behavior, and unconventional superconductivity (SC) [1]. Chandra et al [31] have based their proposal for the HO OP on the Ising-like nature of local 5f moments in URu2Si2 [2], as well as on the recent observation that the quasiparticles in the HO phase exhibit a giant Ising anisotropy [18, 32] They demonstrate that such Ising quasiparticles result from a spinor order parameter that breaks double time-reversal symmetry, mixing states of integer and half-integer spin by hybridizing the conduction electrons with Ising 5f 2 states of the uranium atoms. The detection limit of state-of-the-art neutron scattering no static in-plane magnetic moment exists within the HO phase
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