Adiabatic demagnetization refrigeration (ADR) provides a powerful route to sub-kelvin temperatures and continues to stimulate the search for magnetic refrigerants with optimized thermodynamic properties. The performance of ADR is intimately linked to the magnetic entropy landscape of a material and is therefore strongly influenced by the interplay of exchange interactions, magnetic frustration, and long-range ordering phenomena.

A particular focus of this talk is the role of magnetic frustration in extending the entropy reservoir to very low temperatures. In systems with competing interactions, the suppression of magnetic ordering can preserve substantial entropy, giving rise to broad, field-tunable entropy variations that are highly beneficial for magnetic cooling. Recent studies of rare-earth-based compounds illustrate how geometric frustration and competing exchange interactions can generate favorable conditions for efficient adiabatic demagnetization.

The second part of the presentation addresses an aspect that has recently received renewed attention: the influence of antiferromagnetic ordering on ADR performance. While magnetic ordering has traditionally been regarded as detrimental because it removes entropy from the low-temperature regime, experimental evidence indicates that antiferromagnetic phase transitions can, under suitable conditions, enhance cooling characteristics by extending hold times or improving precooling stages in multistage refrigeration schemes.

By comparing frustrated and ordered magnetic systems, the talk examines the interplay between magnetic entropy and phase transitions in adiabatic demagnetization and considers its implications for the search for improved refrigerant materials.