Ferromagnetic Eu₂SiO₄ Compound with a Record Low-Field Magnetocaloric Effect and Excellent Thermal Conductivity Near Liquid Helium Temperature

Researchers in the field of magnetic refrigeration have recently been chronically committed to the development of magnetic refrigeration materials with a large magnetocaloric effect (MCE) at low magnetic fields. In practice, a brilliant magnetic refrigeration material should not only exhibit a large MCE but also have excellent thermal properties. Therefore, pursuing such an ideal combination in materials becomes a necessity to realize the application of magnetic refrigeration. In this work, a good combination of MCE and thermal properties is presented in the ferromagnetic Eu₂SiO₄ compound. The maximum magnetic entropy change (-Δ<i>S</i>_M^max) reaches an impressive value of 21.6 J·kg^-1·K^-1 under a magnetic field change of 0-1 T, creating a new record for materials in the liquid helium temperature range. Heat capacity data show that the peak value of specific heat reaches 107.9 J·kg^-1·K^-1 near the liquid helium temperature. In addition, this compound exhibits excellent thermal conductivity, with a considerable value of 1.52 W·m^-1·K^-1 at 4.2 K, which surpasses most oxides and is comparable to that of the commercial regenerative material HoCu₂. Remarkable magnetocaloric parameters and thermal properties enable Eu₂SiO₄ to be a promising cryogenic magnetic refrigerant. The magnetic refrigeration experiments further prove it to be a brilliant magnetic refrigerant operating in the liquid helium temperature range.