Rare earth magnetic order in RNi 2B 2C and RNiBC

Abstract

A review of neutron diffraction experiments on the magnetic order in the RNi 2B 2C and RNiBC (R – rare earth) systems is given. The RNi 2B 2C materials exhibit a wide variety of commensurate and incommensurate magnetic structures for different rare earths, along with superconductivity that is coupled to the magnetism. Simple commensurate antiferromagnetic structures are observed for R=Pr (T N =4.0 K) , Nd (T N =4.8 K) , Ho (T N =8.5 K) and Dy (T N =11 K) . In addition, HoNi 2B 2C exhibits a c-axis spiral and an a-axis modulated incommensurate structure above 5 K, while both structures collapse in favor of the commensurate structure at low T. A transversely polarized spin density wave (SDW) type incommensurate structure is observed for Er (T N =6.8 K) and Tm (T N =1.5 K) , while a longitudinally polarized SDW structure is observed for Tb (T N =15 K) . No magnetic ordering of any type is detected for Y, Ce and Yb. HoNiBC is an antiferromagnet (T N =9.8 K) , ErNiBC is ferromagnetic (T C =4.6 K) , while TbNiBC and DyNiBC exhibit both ferromagnetic and antiferromagnetic ordering at 17 K and ∼12 K, respectively.