Magnetic correlations in the S=5/2 quadratic lattice Heisenberg antiferromagnet Mn(HCOO)2･2(ND2)2CO

The magnetic correlations in the quadratic lattice S=5/2 Heisenberg antiferromagnet Mn(HCOO)2⋅2(ND2)2CO (TN=3.77K) have been studied by means of specific heat and neutron-scattering experiments. With a universal temperature scale, the temperature behavior of both the magnetic heat capacity and spin correlations are quantitatively accounted for by the pure quantum self-consistent harmonic approximation by Cuccoli et al. for S=5/2

Specific Heat Study of an S=1/2 Alternating Heisenberg Chain System F_5PNN Under Magnetic Field

We have measured the specific heat of an S=1/2 antiferromagnetic alternating Heisenberg chain pentafulorophenyl nitronyl nitroxide under magnetic fields up to H>H_C2. This compound has the field-induced magnetic ordered (FIMO) phase between H_C1 and H_C2. Characteristic behaviors are observed depending on the magnetic field up to above H_C2 outside of the H-T boundary for the FIMO. Temperature and field dependence of the specific heat are qualitatively in good agreement with the theoretical calculation on an S=1/2 two-leg ladder. [Wang et al. Phys. Rev. Lett 84 5399 (2000)] This agreement suggests that the observed behaviors are related with the low-energy excitation in the Tomonaga-Luttinger liquid.Comment: 4pages, 4figures, replaced with revised version accepted to Physical Review Letter