Hyperfine Field and ⁵¹V Nuclear Relaxation in the Paramagnetic State of the Triangular Lattice Antiferromagnet VX₂ (X=Cl, Br and I)

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The microscopic magnetic properties of the paramagnetic state in the triangular Heisenberg antiferromagnet VX₂ (X=Cl, Br and I) have been investigated by using the NMR technique. From the ⁵¹V shift vs the magnetic susceptibility plot the hyperfine coupling constant due to the d-spin core polarization effect is determined to be −95±2, −79±2 and −69±2 kOe/μ_B for VCl₂, VBr₂ and VI₂, respectively. Also it has been revealed that the high temperature value of the ⁵¹V nuclear spin-lattice relaxation rate is explained from the Guassian model for the auto-correlation function of the spin fluctuations.