Magnetic-field effects on the fragile antiferromagnetism in YbBiPt

We present neutron-diffraction data for the cubic-heavy-fermion YbBiPt that show broad magnetic diffraction peaks due to the fragile short-range antiferromagnetic (AFM) order persist under an applied magnetic-field $H$ . Our results for $H\perp \left[\overline{1}10\right]$ and a temperature of $T=0.14\left(1\right)K$ show that $\left(\frac{1}{2},\frac{1}{2},\frac{3}{2}\right))$ magnetic diffraction peak can be described by the same two-peak line shape found for ${\mathrm{micro}}_{0}H=0T$ below the Néel temperature of $T_N=0.4K$ . Both components of the peak exist for ${\mathrm{micro}}_{0}H\lesssim 1.4T$ , which is well past the AFM phase boundary determined from our new resistivity data. Using neutron-diffraction data taken at $T=0.13\left(2\right)K$ for $H\parallel \left(001\right)$ taken at or $\left(110\right)$ , we show that domains of short-range AFM order change size throughout the previously determined AFM and non-Fermi liquid regions of the phase diagram, and that the appearance of a magnetic diffraction peak at $\left(\frac{1}{2},\frac{1}{2},\frac{1}{2}\right)$ at ${\mathrm{micro}}_{0}H\approx 0.4T$ signals canting of the ordered magnetic moment away from $\left(111\right)$ . The continued broadness of the magnetic diffraction peaks under a magnetic field and their persistence across the AFM phase boundary established by detailed transport and thermodynamic experiments present an interesting quandary concerning the nature of YbBiPt's electronic ground state.