Functional Micro‐Scaled Er ₇₃ Pr ₂₇ Alloy for Magnetic Refrigeration: Cooling Efficiency and Mechanical Reliability

The performance of regenerative cryocoolers depends critically on magnetic regenerator materials. Large volumetric specific heat combined with high mechanical strength enables stable and efficient refrigeration performance. As magnetic regenerator materials are typically employed as spherical particles, their microscale properties are particularly important. Here, we explored the origin of the high heat capacity of Er 73 Pr 27 alloys by magnetic measurements. A Stirling‐cycle model further demonstrated that a cooling power of 2.72 W is performed for Er 73 Pr 27 spheres at 20 K, comparable to commercial regenerator alloys, e.g., Er 3 Ni and HoCu 2 . To assess the mechanical reliability, micropillar compression tests were conducted on Er 73 Pr 27 spheres. Governed by a dislocation‐starvation mechanism, the yield strength exhibits a strong size dependence, which increases from 222 MPa at 2 µm to 819 MPa at 0.4 µm. These findings highlight Er 73 Pr 27 as a promising cryogenic regenerator material and provide insights into designing mechanically robust magnetic regenerator alloys for cryocoolers.