Abstract
Unlike conventional magnetic states, which lack degeneracy, the spiral spin liquid (SSL) fluctuates among degenerate spiral configurations, with ground-state wave vectors forming a continuous contour or surface in reciprocal space. At low temperatures, the field-induced crossover from the polarized ferromagnetic state to the SSL results in a large entropy increase and decalescence, indicating its potential for magnetic cooling. However, magnetic cooling using a SSL has yet to be reported. Here, the magnetocaloric effect and cooling performance of single-crystal GdZnPO, a spin-7/2 honeycomb-lattice SSL candidate, are investigated under a magnetic field H < H(c) (µ(0)H(c) ∼ 12 T) applied perpendicular to the honeycomb plane and below the crossover temperature (∼2 K). For H ⩾ H(c), GdZnPO enters a polarized non-degenerate ferromagnetic state. These results demonstrate that GdZnPO exhibits a giant low-temperature magnetocaloric effect near H(c), surpassing other magnetocaloric materials. This giant magnetocaloric effect is well-explained by the frustrated honeycomb spin model of GdZnPO, suggesting the stability of the SSL below H(c) down to very low temperatures. Additionally, its magnetic cooling performance remains robust up to at least 4.5 K, making GdZnPO a promising candidate for magnetic refrigeration down to ∼36 mK through cycling the applied magnetic field within a narrow range.