Heat capacity and hidden energy scale in geometrically frustrated magnets

The low-temperature properties of geometrically frustrated antiferromagnets generically exhibit the ``hidden energy scale'' T^*, which manifests itself in the heat capacity, neutron scattering, and in a broad class of materials, in the spean freezing at temperatures below the scale T^*.

(c) 2026 Sergey Syzranov

This simulation shows the qualitative behavior of the heat capacity C(T) in a geometrically frustrated antiferromagnet. C(T) generically exhibits two peaks, with the higher- and lower-temperature peaks located at the Curie-Weiss temperature θ_CW and the "hidden energy scale" T^*. C(T) is shown qualitatively and may deviate from the data in particular materials. Continous deformations of the model change the T^*/θ_CW ratio, which can be controlled with the slider above. The Ising limit corresponds to T^*/θ_CW=0; T^*/θ_CW> 0 corresponds to quantum XXZ antiferromagnets.

For the discussion of the microscopic details of the heat capacity and the hidden energy scale, please see

• Siyu Zhu, Arthur P. Ramirez, and Sergey Syzranov, "Low-temperature entropies and possible states in geometrically frustrated magnets", arXiv:2511.02899
• Phillip Popp, Arthur P. Ramirez, and Sergey Syzranov, "Short-range order and hidden energy scale in geometrically frustrated magnets", Phys. Rev. Lett. 134, 226701 (2025)
• A.P. Ramirez and S.V. Syzranov, "High-Dimensional Short-range order and hidden energy scale in geometrically frustrated magnets", a review article,
  Mater. Adv. 6, 1213 (2025)