A series of layered lanthanide phosphonates alpha-Ln(2-qpH)(SO4)(H2O)(2) (alpha-Ln; Ln = Gd, Tb, Ho, Er) and beta-Ln(2-qpH)(SO4)(H2O)(2) (beta-Ln; Ln = Gd, Tb, Ho, Er, Yb) (2-qpH(2) = 2-quinolinephosphonic acid) have been synthesized and characterized. Compounds alpha-Ln crystallize in monoclinic space group P2(1)/c, while compounds beta-Ln crystallize in triclinic space group P (1) over bar. Magnetic studies reveal that dominant ferromagnetic interactions are propagated between the magnetic centers in all cases. Field-induced magnetic relaxation is observed in compounds beta-Er and beta-Yb.