Magnetic properties ofDyB2C,HoB2C,andErB2C

Abstract

Magnetic properties of layered borocarbides $R{\mathrm{B}}_{2}\mathrm{C}$ $(R=\mathrm{Dy},$ 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. ${\mathrm{ErB}}_{2}\mathrm{C}$ has a basic two-sublattice antiferromagnetic order below ${T}_{\mathrm{N}}=16.3\mathrm{K}.$ ${\mathrm{HoB}}_{2}\mathrm{C}$ and ${\mathrm{DyB}}_{2}\mathrm{C}$ show the three-dimensional magnetic order below ${T}_{\mathrm{C}}=7.0\mathrm{K}$ and 8.5 K, respectively. However, they have still large magnetic fluctuations below ${T}_{\mathrm{C}}.$ The magnetic ordering temperatures of $R{\mathrm{B}}_{2}\mathrm{C}$ $(R=\mathrm{Dy},$ Ho, and Er) do not follow the de Gennes relation, where the ordering temperatures of ${\mathrm{HoB}}_{2}\mathrm{C}$ and ${\mathrm{DyB}}_{2}\mathrm{C}$ are suppressed. The suppressions of ordering temperature and the unconventional fluctuating ground states of ${\mathrm{HoB}}_{2}\mathrm{C}$ and ${\mathrm{DyB}}_{2}\mathrm{C}$ 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.