Review of magnetic features observed in (A,A′)Ni2B2C solid solutions

The nickel-borocarbides ANi(2)B(2)C [A = Y,Ln (lanthanide), An(actinide)], crystallizing in the body-centred tetragonal LuNi2B2C-type structure, are classified according to the existence or coexistence of superconducting and antiferrornagnetic states (AF). The magnetic features observed in polycrystalline (A,A')Ni2B2C solid solutions, adopting the same crystal structure, are reviewed and discussed. Published data on the magnetism in (A, Ln)Ni2B2C systems (ANi(2)B(2)C nonmagnetic, A=Y,La,Lu) indicate a gradual rise in the threshold content, x(m), in (Y(1-x)Ln(x))Ni2B2C (Ln=Gd,Tb, Dy,Ho,Er) for the establishment of AF states. (A,A')Ni2B2C systems with magnetic end compounds show gradual variation in magnetic features when A and A' are both heavy Ln. The behaviour of (A,A')Ni2B2C systems of light A (Pr or U) and heavy A' (Dy or Tm) depends on the magnetic structures of the end compounds. In intermediate compositions, incomplete moment compensation in (Pr,Dy)Ni2B2C decreases T-N, while different moment directions in the end compounds in (U,Dy)Ni2B2C lead to a directional frustration of ordered moments. Such a frustration in (U,Tm)Ni2B2C is related to different magnetic structures of the end compounds. (C) 2002 Elsevier Science B.V. All rights reserved.