Fragile antiferromagnetic order in the heavy-fermion YbBiPt

YbBiPt is a heavy-fermion compound ($\gamma\approx$ 8 J/molK$^2$) possessing antiferromagnetic order below a N\'{e}el temperature of $T_{\rm{N}}$= 0.4 K, and a proposed quantum critical point at a magnetic field of $H_{\rm{c}}\approx$ 0.4 T. We report results from neutron scattering experiments on single crystals which characterize the antiferromagnetic order. The magnetic scattering is described in terms of two components: a narrow component that appears below $T_{\rm{N}}$ which corresponds to the onset of antiferromagnetic order observed in bulk thermodynamic and transport measurements, and a broad component corresponding to antiferromagnetic correlations extending over $\approx$ 20 $\rm{\AA}$ that persists up to $T^{\rm{*}}\approx$ 0.7 K. These results illustrate the unconventional nature of the magnetism in YbBiPt and may be a consequence of its competing low-energy magnetic interactions and proximity to a quantum critical point.\\ Work at the Ames Laboratory was supported by the Department of Energy, Basic Energy Sciences under Contract No. DE-AC02-07CH11358.