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Specific heat of the $S = 1$ spin-dimer antiferromagnet Ba$_3$Mn$_2$O$_8$ in high magnetic fields

H. Tsujii·B. Andraka·M. Uchida·H. Tanaka·Y. Takano
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Abstract

We have measured the specific heat of the coupled spin-dimer antiferromagnet Ba$_3$Mn$_2$O$_8$ to 50 mK in temperature and to 29 T in the magnetic field. The experiment extends to the midpoint of the field region (25.9 T $\leq H \leq$ 32.3 T) of the magnetization plateau at 1/2 of the saturation magnetization, and reveals the presence of three ordered phases in the field region between that of the magnetization plateau and the low-field spin-liquid region. The exponent of the phase boundary with the thermally disordered region is smaller than the theoretical value based on the Bose-Einstein condensation of spin triplets. At zero field and 29 T, the specific-heat data show gapped behaviors characteristic of spin liquids. The zero-field data indicate that the gapped triplet excitations form two levels whose energies differ by nearly a factor of two. At least the lower level is well localized. The data at 29 T reveal that the low-lying excitations at the magnetization plateau are weakly delocalized.

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H. Tsujii, B. Andraka, M. Uchida, H. Tanaka, Y. Takano. 2005-11-04. Specific heat of the $S = 1$ spin-dimer antiferromagnet Ba$_3$Mn$_2$O$_8$ in high magnetic fields. https://doi.org/10.1103/physrevb.72.214434

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