Magnetic phase transition and magnetocaloric effect in Mn–Fe–Ni–Ge ribbons

•Mn–Fe–Ni–Ge ribbon samples are prepared.•Ferromagnetic interaction is established in these ribbons.•Double first-order magnetic phase transitions are observed in these two ribbons.•The coupled magnetostructural transformation is achieved in these ribbons.•Giant magnetocaloric effect near room temperature is obtained in these ribbons.

Two Mn–Fe–Ni–Ge ribbon samples are prepared. Due to the inherent antiferromagnetic (AFM) interaction and its instability, the Fe-substitution induces the magnetic-field-induced AFM-ferromagnetic (FM) conversion and then, the competition between the established FM coupling and the intrinsic AFM interaction triggers the first-order AFM–FM magnetoelastic transition in TiNiSi-type state for these two ribbons. When the AFM–FM conversion completes, the coupled magnetostructural transformation from the FM TiNiSi-type to paramagnetic Ni2In-type state with large magnetocaloric effect near room temperature is achieved in these two ribbons.