The magnetic and magnetocaloric properties of CoMnGe1−xGax alloys

The magnetic and magnetocaloric properties of CoMnGe1−xGax (0.02 ⩽ x ⩽ 0.063) alloys have been investigated by using calorimetric, X-ray diffraction and magnetic measurements. Our results show that the structural and magnetic phase transitions in CoMnGe1−xGax alloys are tailored by the substitution of Ga for Ge. The CoMnGe1−xGax (x = 0.05, 0.055 and 0.06) alloys exhibit a giant magnetocaloric effect due to coexistence of magnetic and Martensitic phase transitions at the same temperatures. The entropy change values range from −3.2 to −38.4 J kg−1 K−1 for Δ H = 7 T and are proportional to the volume differences of the phases involved in the transition. The adiabatic temperature change value of CoMnGe0.945Ga0.055 is calculated as 6.5 K for the magnetic field change of 2 T from magnetic and heat capacity measurements. The density of states of electrons at Fermi level and the Debye temperature values of this alloy are found 1.37 states eV−1 atom−1 and 337 K from low temperature heat capacity measurements.