Unconventional Magnetic Correlations in DyB2C and HoB2C

Abstract

Layered borocarbides RB2C (R=Dy,Ho,and Er) have been studied by powder neutron diffraction at 2–30 K. ErB2C has two-sublattice antiferromagnetic order below TN= 16:3 K, but DyB2C and HoB2C show a coexistence of a conventional canted k = (000) ferromagnetic structure and unconventional magnetic correlations. The k = (000) phase orders at Tc = 8:5 K (DyB2C) and 7.1 K (HoB2C), but low-Q diffraction peaks from the unconventional correlations appear above Tc with different critical temperatures for different peaks: at 8, 10.5, and 15.7 K for HoB2C. This scattering is fitted as diffraction from a Warren-type random magnetic layer lattice and may result from quadrupolar interactions between R3+ spins.