  High temperature one-dimensional (1D) ferromagnetic (FM) chains in Ca3Co2O6
spin system are subjected to a magnetic field and temperature induced first
order phase transition (FOPT) to 3D ferrimagnetic (FIM) ground state with
decrease in temperature (T). Weak-FM interaction of third nearest-neighbor(nn)
interchain removes the frustration effect arising from antiferromagnetic (AFM)
interactions of first-nn and second-nn interchains in the underlying
triangular-lattice resulting a 3D FIM ordering of 1D FM chains at low T.
However, hindered kinetics of FOPT partially masks this tranformation giving
rise to coexistence of non-interacting 1D FM chains with 3D-FIM state at low-T.
The existence of all these couplings is further confirmed here by random
substitution of S = 5/2 magnetic-impurity into the spin chain of original
system. It reveals weakening of FM interactions of both intrachain and third-nn
surrounding chains respectively without significant modulation in the AFM
coupling of first-nn and second-nn interchains. Thus, influence of AFM
interactions is enhanced as compared to effective FM coupling with increase of
S = 5/2 impurity content resulting instability of 3D long-range FIM state at
low-T.
