A Novel Look at Magnetism in Ni2FeVO6

DC magnetometry and electron spin resonance (ESR) studies of Ni2FeVO6 powder samples obtained by the traditional calcination method are presented. As our X-ray diffraction study of Ni2FeVO6 has revealed an orthorhombic crystal structure and not previously reported rhombohedral FeTiO3-type structure (ilmenite), a new magnetic structure was proposed. As a consequence, the role of magnetic ions had to be re-evaluated. The transition to ferromagnetic (FM)-like phase was found at T-C = 200 K in weak magnetic fields, while spin freezing dynamics in the superparamagnetic (SPM) regime was observed below TC. Above 260 K, the Curie-Weiss paramagnetic (PM) phase with a large effective magnetic moment mu(eff) = 11.7 mu(B)/f.u was found. Interestingly, the Griffiths phase (GP) above T-C was also detected. The important role of magnetic spin clusters with different sizes has been inferred from magnetization measured in different magnetic fields and at different temperatures. Although the main bulk ferromagnetic phase was not registered in the ESR spectra, they were analyzed in terms of Lorentzian and Gaussian components and attributed to different types of PM spin clusters with FM and antiferromagnetic (AFM) interactions.