Strict limit on in-plane ordered magnetic dipole moment in URu2Si2

Neutron diffraction is used to examine the polarization of weak static antiferromagnetism in high quality single crystalline URu2Si2. As previously documented, elastic Bragg-like diffraction develops for temperature T < T-HO = 17.5 K at q = (100) but not at wave vector transfer q = (001). The peak width indicates correlation lengths xi(c) = 230(12) angstrom and xi(a) = 240(15) angstrom. The integrated intensity of the T-dependent peaks corresponds to a sample averaged c-oriented staggered moment of mu(c) = 0.022(1) mu(B) at T = 1.7 K. The absence of T-dependent diffraction at q = (001) places a limit mu(1) < 0.0011 mu(B) on an f - or d-orbital-based in-plane staggered magnetic dipole moment, which is associated with multipolar orders proposed for URu2Si2.