Magnetic properties ofDyB2C,HoB2C,andErB2C

Magnetic properties of layered borocarbides RB₂C (R=Dy, Ho, and Er) have been studied by the magnetization and specific heat measurements at 1.8–300 K under the field up to 5 T. ErB₂C has a basic two-sublattice antiferromagnetic order below T_N=16.3K. HoB₂C and DyB₂C show the three-dimensional magnetic order below T_C=7.0K and 8.5 K, respectively. However, they have still large magnetic fluctuations below T_C. The magnetic ordering temperatures of RB₂C (R=Dy, Ho, and Er) do not follow the de Gennes relation, where the ordering temperatures of HoB₂C and DyB₂C are suppressed. The suppressions of ordering temperature and the unconventional fluctuating ground states of HoB₂C and DyB₂C originate from the spin frustration effects. The instability of the unconventional magnetic phase associated with the frustration is significant in this series; the fluctuating ground state results from the complex spin–spin interactions or spin–quadrupole interactions.