Large magnetocaloric effect and adiabatic demagnetization refrigeration with YbPt₂Sn

Adiabatic demagnetization is currently gaining strong interest in searching for alternatives to 3He-based refrigeration techniques for achieving temperatures below 2[thinsp]K. The main reasons for that are the recent shortage and high price of the rare helium isotope 3He. Here we report the discovery of a large magnetocaloric effect in the intermetallic compound YbPt2Sn, which allows adiabatic demagnetization cooling from 2[thinsp]K down to 0.2[thinsp]K. We demonstrate this with a home-made refrigerator. Other materials, for example, paramagnetic salts, are commonly used for the same purpose but none of them is metallic, a severe limitation for low-temperature applications. YbPt2Sn is a good metal with an extremely rare weak magnetic coupling between the Yb atoms, which prevents them from ordering above 0.25[thinsp]K, leaving enough entropy free for use in adiabatic demagnetization cooling. The large volumetric entropy capacity of YbPt2Sn guarantees also a good cooling power