Magnetic susceptibility of vanadium garnets NaPb2Co2V3O12 and NaPb2Ni2V3O12 Original Research Article

Vanadium garnets NaPb2Co2V3O12 and NaPb2Ni2V3O12 have been successfully synthesized. The X-ray diffraction experiments indicate that these compounds have the garnet structure of cubic symmetry of space group View the MathML sourceIa3¯dView the MathML source(Oh10) with the lattice constant of 12.742 Å (NaPb2Co2V3O12) and 12.666 Å (NaPb2Ni2V3O12), respectively. The magnetic susceptibility of NaPb2Ni2V3O12 shows the Curie–Weiss paramagnetic behavior between 4.2 and 350 K. The effective magnetic moment μ eff of NaPb2Ni2V3O12 is 3.14 μ B due to Ni2+ ion at A-site and the Weiss constant is −3.67 K (antiferromagnetic sign). For NaPb2Co2V3O12, the simple Curie–Weiss law cannot be applicable. The ground state is the spin doublet View the MathML sourceE2(t26e) and the first excited state is spin quartet View the MathML sourceT14(t25e2), according to Tanabe–Sugano energy diagram on the basis of octahedral crystalline symmetry. This excited spin quartet state just a bit higher than ground state influences strongly the complex temperature dependence of magnetic susceptibility for NaPb2Co2V3O12.