Giant magnetocaloric effect in a rare-earth-free layered coordination polymer at liquid hydrogen temperatures

Magnetic refrigeration, using the magnetocaloric effect, offers a sustainable alternative to conventional cooling methods. This study investigates Co₄(OH)₆(SO₄)₂[enH₂], a rare-earth-free layered coordination polymer, for cryogenic applications such as hydrogen liquefaction. Measurements reveal a large magnetocaloric effect near the hydrogen liquefaction temperature (10 K < *T_C* < 15 K), with Δ*S*_M^max = −6.31 J kg⁻¹ K⁻¹ and Δ*T*_ad = 1.98 K for a 1 T field change. These values are exceptional for rare-earth-free materials and compete with many rare-earth-containing alloys.

J. J. B. Levinsky, B. Beckmann, T. Gottschall, D. Koch, M. Ahmadi, O. Gutfleisch, G. R. Blake