Synthesis, structure and properties of R NiBN ( R = rare-earth elements)

We report the structural and physical properties of new nitridoborates R NiBN ( R = Nd, Sm, Gd, Tb, Dy, Ho, and Er). These compounds crystallize in a tetragonal LaNiBN-type structure with two-dimensional Ni 2 B 2 and R N layers. The physical properties measurements indicate that they are antiferromagnetic metals. For R = Gd and Ho, a successive magnetic transition was observed below N é el temperature, possibly associated with spin re-orientation due to Ruderman-Kittel-Kasuya-Yosida interaction. A giant magnetocaloric effect was measured in the R = Er and Ho compounds, which is related to a field-induced first-order metamagnetic transition from antiferromagnetic to ferromagnetic state. Our results indicate that R NiBN ( R = Er and Ho) may be promising candidates for low temperature magnetic refrigeration