Polymorphic Lanthanide Phosphonates Showing Distinct Magnetic Behavior

A series of layered lanthanide phosphonates α-Ln­(2-qpH)­(SO₄)­(H₂O)₂ (α-Ln; Ln = Gd, Tb, Ho, Er) and β-Ln­(2-qpH)­(SO₄)­(H₂O)₂ (β-Ln; Ln = Gd, Tb, Ho, Er, Yb) (2-qpH₂ = 2-quinolinephosphonic acid) have been synthesized and characterized. Compounds α-Ln crystallize in monoclinic space group P2₁/c, while compounds β-Ln crystallize in triclinic space group P1̅. Magnetic studies reveal that dominant ferromagnetic interactions are propagated between the magnetic centers in all cases. Field-induced magnetic relaxation is observed in compounds β-Er and β-Yb.