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.