We have performed high-field multi-frequency electron spin resonance (ESR) measurements of a single crystal of the S = 1/2 quasi one-dimensional (1D) Ising-like antiferromagnet BaCo2V2O8 at 1.5 K in magnetic fields of up to 14 T applied along  and  directions. Two main ESR branches, which are ascending and descending with increasing magnetic fields, are observed from 400 GHz at zero magnetic field in both cases. The low ESR mode shows a softening near 10 T for H || , while no softening was observed below 14 T for H || . This difference in the magnetic excitations may explain the distinct phase diagrams for these two directions.
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