First-order magnetostructural transformation in Fe doped MnaCoaGe alloys

Substitution of Fe for Mn atoms in MnaCoaGe alloys was employed for tailoring concurrent structural and magnetic phase transitions. First-order magnetostructural transition from paramagnetic hexagonal Ni2In-type parent phase to ferromagnetic orthorhombic TiNiSi-type martensite was achieved. A giant magnetocaloric effect of a3Sm = a9.74 J kga1 Ka1 was obtained under magnetic field change of 5 T in the vicinity of phase transition temperature. This result indicates that Fe doped MnaCoaGe alloys are ideal candidates for magnetic refrigeration applications. Furthermore, the magnetic field-induced martensitic transformation, associated with a large lattice strain of a1412%, was directly evidenced by in situ synchrotron high-energy X-ray diffraction.