Giant Low-Field Magnetocaloric Effect in the Superlattice Antiferromagnetic ErFe₂Si₂ Compound

We present herein a systematic study of a polycrystalline magnetocaloric compound ErFe₂Si₂. It exhibits a transition from the antiferromagnetic to the paramagnetic phase around 3.0 K according to magnetic and heat capacity measurements. Neutron powder diffraction revealed that ErFe₂Si₂ possesses a superlattice magnetic structure with a propagation vector of (0, 0, 0.5). The superlattice magnetic structure can be modeled by a transverse spin density wave (cosine-modulated) or a spiral type, which cannot be distinguished solely by neutron powder diffraction (NPD) pattern fitting. The stability of different types of magnetic structures was also investigated by first-principles calculations. The ErFe₂Si₂ compound shows a giant magnetocaloric effect with a maximal negative magnetic entropy change and an adiabatic temperature change of 11.5 J/kg K and 5.7 K, respectively, under the field change of 0–1 T. The large low-field magnetocaloric effect is related to its low critical field of metamagnetic transition and its low quasi-saturation magnetic field. The excellent performance of ErFe₂Si₂ makes this compound a potential magnetocaloric material for applications at liquid helium temperatures.