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 perpendicular to[(1) over bar 1 0] and a temperature of T = 0.14(1) K show that the (1/2,1/2,3/2) magnetic diffraction peak can be described by the same two-peak line shape found for mu H-0 = 0T below the Neel temperature of T-N = 0.4 K. Both components of the peak exist for mu H-0 less than or similar to 1.4 T, which is well past the AFM phase boundary determined from our new resistivity data. Using neutron-diffraction data taken at T = 0.13(2)K for H parallel to [0 0 1] or [1 1 0], 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 (1/2,1/2,1/2) at mu H-0 approximate to 0.4T signals canting of the ordered magnetic moment away from [1 1 1]. 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.