Entropy Constraints in the Ground State Formation of Magnetically Frustrated Systems: Role of Nernst Postulate in Real Systems

Abstract

A systematic modification of the entropy trajectory (Sm(T)) is observed at very low temperature in magnetically frustrated systems as a consequence of the constraint (Sm≥ 0) imposed by the Nernst postulate. The lack of magnetic order allows to explore and compare new thermodynamic properties by tracing the specific heat (Cm) behavior down to the sub-Kelvin range. Some of the most relevant findings are: (i) a common Cm/ T| T → 0≈ 7 J/mol K2 ‘plateau’ in at least five Yb-based very-heavy-fermions (VHF) compounds; (ii) quantitative and qualitative differences between VHF and standard non-Fermi-liquids; (iii) entropy bottlenecks governing the change of Sm(T) trajectories in a continuous transition into alternative ground states. A comparative analysis of Sm(T→ 0) dependencies is performed in compounds suitable for adiabatic demagnetization processes according to their ∂2Sm/ ∂T2 derivatives.