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 . Our results for and a temperature of show that magnetic diffraction peak can be described by the same two-peak line shape found for below the Néel temperature of . Both components of the peak exist for , which is well past the AFM phase boundary determined from our new resistivity data. Using neutron-diffraction data taken at for taken at or , 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 at signals canting of the ordered magnetic moment away from . 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.