Magnetism and superconductivity in (RE) Ni2B2C: The case of TmNi2B2C

Abstract The recently reported coexistence of an oscillatory magnetic order with wave vector Q = 0.241 −1 and superconductivity in TmNi 2 B 2 C is analyzed theoretically. It is shown that the oscillatory magnetic order and superconductivity interact predominantly via the exchange interaction between localized moments (LMs) and conduction electrons, while the electromagnetic interaction between them is negligible. In the coexistence phase of the clean TmNi 2 B 2 C the quasiparticle spectrum should have a line of zeros at the Fermi surface, giving rise to the power-law behavior of thermodynamic and transport properties. Two scenarios of the origin of the oscillatory magnetic order in TmNi 2 B 2 C are analyzed: (a) due to superconductivity and (b) independently of superconductivity. Experiments in a magnetic field are proposed in order to choose between them.