Heavy-fermion weak-ferromagnet YbRhSb

Abstract

A new Yb-based compound YbRhSb with the orthorhombic $\ensuremath{\varepsilon}$-TiNiSi-type structure has been synthesized. The magnetic-susceptibility, magnetization, and specific-heat ${(C}_{p})$ measurements of single crystals revealed a ferromagnetic transition at ${T}_{C}=2.7\mathrm{K}.$ An extrapolation of the ${C}_{p}/T$ data below 1 K yields $370{\mathrm{m}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{}\mathrm{K}}^{2}$ as the $\ensuremath{\gamma}$ value, and the magnetic entropy reaches only $0.25R\mathrm{ln}2$ at ${T}_{C}.$ The spontaneous moment is unusually small, $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{\ensuremath{\mu}}_{\mathrm{B}}/\mathrm{Yb}$ for $B||b,$ while the magnetization increases to $1.4{\ensuremath{\mu}}_{\mathrm{B}}/\mathrm{Yb}$ when the field of 15 T is applied along the a axis. We ascribe the weak ferromagnetism to a canted antiferromagnetic structure based on the observation of a metamagnetic transition and the decrease of ${T}_{C}$ with the increase of magnetic field.