Pressure effects of an S = 1 Heisenberg antiferromagnetic bond alternating chain

By the measurement of magnetic susceptibility under pressures (P) up to 8 kbar, we investigated pressure effects of the S = 1 Heisenberg antiferromagnetic bond alternating chain compound [{Ni(333-tet)(μ-N₃)}_n](ClO₄)_n (333-tet denotes N,N′-bis(3-aminopropyl)-1,3-propanediamine), whose alternating interaction ratio (α) at ambient pressure is very close to the theoretical value for the gapless point (α_c, ≃ 0.59). There are two kinds of intrachain interactions due to bond alternation (J₁ and J₂), both of which are increased linearly against the pressure. At P = 8 kbar those magnitudes exceed 1.4 times of those at ambient pressure. The magnitude of α = J₂/J₁, however, does not change largely. The normalized magnetic susceptibility χ|J₁|k_B around k_BΤ/\J₁\ = 0.1 has the maximum value at P = 2 kbar, and this suggests the possibility of the slight changes of α and D.