Anisotropic magnetic properties of TbNi2B2C single crystals.

Abstract

Magnetic and transport properties of single crystals of ${\mathrm{TbNi}}_{2}$${\mathrm{B}}_{2}$C have been investigated by ac susceptibility, dc magnetization, specific heat, and resistance measurements. The compound shows highly anisotropic magnetic properties which come about as a result of the Tb magnetic moments lying predominantly in the ab plane. The ac susceptibility and low-field dc magnetization measurements indicate the presence of two magnetic transitions; one due to the antiferromagnetic (AFM) ordering of the Tb moments around 15 K, and another at 5 K, which we believe is due to a spin reorientation of the Tb moments. The resistivity (${\mathrm{\ensuremath{\rho}}}_{\mathit{ab}}$) measurements show a sharp decrease in the resistance at 15 K but contain no observable features corresponding to the lower-temperature transition. The compound does not show superconductivity above 300 mK. Specific heat at low temperatures shows a large \ensuremath{\lambda}-type anomaly at 13.8 K in addition to the anomalies associated with the AFM ordering of the Tb moments at 15 K (${\mathit{T}}_{\mathrm{AF}}$) and the spin reorientation at 5 K. Magnetization (M) and ${\mathrm{\ensuremath{\rho}}}_{\mathit{ab}}$(T) measurements indicate a decrease in ${\mathit{T}}_{\mathrm{AF}}$ as a function of applied field (H) for H\ensuremath{\parallel}ab, whereas for H\ensuremath{\parallel}c, ${\mathit{T}}_{\mathrm{AF}}$ is independent of field. The M-H isotherms at 2 K show that for H\ensuremath{\parallel}ab the compound goes through a series of temperature-dependent metamagnetic states before finally saturating into a ferromagnetic state for H\ensuremath{\gtrsim}21 kOe. For H\ensuremath{\parallel}c the compound shows a linear M-H behavior expected for a normal AFM compound. The ${\mathrm{\ensuremath{\rho}}}_{\mathit{ab}}$(H) measurements show anomalies due to the metamagnetic transitions and a large negative magnetoresistance above 21 kOe for H\ensuremath{\parallel}ab. \textcopyright{} 1996 The American Physical Society.