The magnetic state of the V$^{3+}$ ions in ferrites with the spinel structure

The magnetization Is and coercive force Hс of ferrites of the system $NiFe_{2-x}VxO_{4}$ where x = 0.00, 0.25, 0.50, 0.67, 0.80 and 1.00 are invesdtigated. The effective value of the magnetic anisotropy constants are found for all the specimens using the equation |K$_eff$| = 4ПIsHс at 80K. It is shown that the contribution of the $V^{3+}_B$ ions to the magnetic anisotropy is small and has a positive sign. It is suggested that in the crystal field of an octahedral complex the orbital triplet of the $V^{3+}$ ion is split in such a way that the orbital singlet becomes lower.