Low dimensional magnetism of M(VOPO4)2·4H2O layered compounds: the 2D ferromagnet Cd(VOPO4)2·4H2O and the 2D antiferromagnet Mg1–xZnx(VOPO4)2·4H2O with x≈0.28

Abstract

A magnetic study has been carried on the non-magnetic cations intercalated vanadyl phosphates Cd(VOPO ₄ ) ₂ ·4H ₂ O and Mg _1–x Zn _x (VOPO ₄ ) ₂ ·4H ₂ O with x≈0.28. The susceptibility measurements are indicative of weak magnetic interactions within the negatively charged [VO _4/2 OPO _4/2 ] ^{∞ –} layers, which are interpreted on the basis of a 2D square planar Heisenberg model. Cd(VOPO ₄ ) ₂ ·4H ₂ O is ferromagnetic with J=+0.87 cm ^–1 while Mg _0.72 Zn _0.28 (VOPO ₄ ) ₂ ·4H ₂ O is antiferromagnetic (J=–1.93 cm ^–1 ). The obtained results are discussed in connexion with the structural features.