Three-dimensional unfrustrated and frustrated quantum Heisenberg magnets. Specific heat study

We examine the S = 1/2 Heisenberg magnet on four three-dimensional lattices — simple-cubic, diamond, pyrochlore, and hyperkagome ones — for ferromagnetic and antiferromagnetic signs of the exchange interaction in order to illustrate the effect of lattice geometry on the finite-temperature thermodynamic properties with a focus on the specific heat c(T). To this end, we use quantum Monte Carlo simulations or high-temperature expansion series complemented with the entropy method. We also discuss a recent proposal about hidden energy scale in geometrically frustrated magnets.