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The aim of the paper was to synthesize a series of LnIII2(Ln = Gd, Tb, Dy, and Ho) complexes that offer a great perspective to construct functional magnetic materials. Here, we have ventured a Schiff base ligand by combining 2,6-diformyl-4-methylphenol with 2-hydroxy-benzoic acid hydrazide, and the ligand is reacted with Ln(NO3)3·6H2O (1:1), which affords [Ln2(H2L)3](NO3)3(Ln = Gd, Dy, and Ho) and [Ln2(H2L)3](NO3)3(CH3OH) (Ln = Tb) complexes. Structural analyses illustrate that the four complexes have a stoichiometry of 2:3 (M:L), wherein three phenolic oxygen atoms are simultaneously coordinated with two metal atoms to form LnIII–Ophenoxo–LnIIIbridges. Variable-temperature magnetic susceptibility measurements have been performed in the 2–300 K region for all of the compounds. Magnetic studies indicate that the DyIII2analogue exhibits the slow relaxation of magnetization behavior under 700 Oe external dc field with an energy barrier of 2.97–7.73 K. The alternating current (ac) magnetic susceptibility measurements were also performed on the 90:10 (Y:Dy) diluted sample analogue and they depicted that the slow magnetic relaxation properties originated mostly from the single ion but not the coupling between DyIIIions. The best-fitting results provided Ueffvalues of 1.61–2.90 K with τ0values of 1.31 × 10–5–6.97 × 10–4s for the diluted sample of DyIIIunder 500 Oe dc field.