Magnetostructural phase transitions and magnetocaloric effects in as-cast Mn1-xAlxCoGe compounds

The structural and magnetic properties of as-cast Mn1-xAlxCoGe (0 ≤ x ≤ 0.05) have been studied by X-ray diffraction, differential scanning calorimetry, and magnetization measurements. The partial substitution of Al for Mn in Mn1-xAlxCoGe results in a decrease in the martensitic transition temperature TM. For the concentration range 0 ≤ x ≤ 0.01, TM was found to coincide with ferromagnetic transition temperature (TC) resulting in a first-order magnetostructural transition (MST). A further increase in aluminum concentration resulted in a splitting of the phase transition temperatures, which included a drastic decrease in the martensitic temperature. The compounds with x > 0.02 showed a single transition at TC. The maximum values of the magnetic entropy changes (-ΔSM) were ∼18 J/kgK, 12 J/kgK, and 7 J/kgK for ΔH = 5T at 313 K (x = 0.00), 286 K (x = 0.01), and 220 K (x = 0.02), respectively. The maximum value of the relative cooling power (RCP) was found to be 303 J/kg for x = 0.01 at T = 286 K for ΔH = 5T. It has been established that as-cast samples of this system show large value of MCE near room temperature making this system a promising material for magnetic cooling technologies.