Sr2Cu(PO4)2 and Ba2Cu(PO4)2 as quasi-one-dimensional spin-12 Heisenberg antiferromagnet

Using magnetic exchange couplings for antiferromagnets Sr ₂Cu(PO ₄) ₂ and Ba ₂Cu(PO ₄) ₂, estimated independently by Johannes (2006 [1]) and Salunke (2007 [2]), we present model calculations via exact diagonalization for several lattices of 24 and 16 spins by calculating experimentally accessible quantities like spin–spin correlation, the antiferromagnetic order-parameter, entropy-density, specific-heat and z -component of the magnetic susceptibility using up to 15 low-lying eigenstates. From our calculation, the ratio of critical entropy and mean-field critical entropy comes out to be ∼ 0.492 ( 7 ) . The slope of the specific heat curve at low temperatures is found to be 2 / 3 . The peak value of z -component of the magnetic susceptibility versus temperature curve turns out to be 1 3 χ ∼ 0.05 . Our results favor the conclusion that these magnetic compounds are indeed quasi-one-dimensional antiferromagnets.