Crystal growth, magnetic property and phase transition of the zigzag-chain antiferromagnet FeNbO4

We report crystal growth, magnetic properties and electron spin resonance (ESR) study of the one dimensional zigzag-chain compound FeNbO4. The single crystals were grown by the flux method using Na2WO4·12H2O and Na2W2O7 as the flux. Magnetic susceptibility and specific heat data show an antiferromagnetic ordering below 44 K. High-field magnetization data reveal a spin-flop transition at 12 T when magnetic field is applied along the magnetic easy axis. Multi-frequency ESR study on the single crystals reveal three resonance modes which can be understood by the molecule-field theory. Using a simple model with easy-axis type anisotropy, we estimate that the anisotropy field HA and the exchange field HE are 2.67 T and 27 T, respectively. The zero-frequency resonance field at 11 T corresponds to the spin-flop transition, demonstrating a close correlation between the high-field magnetization and the ESR spectra.