Magnetocaloric properties of ternary Al-Mn-Co alloys

We investigate how the Al content in Al x (Mn 0.76 Co 0.24 ) 1-x (x=0.45, 0.50, 0.55) alloys and the Mn/Co ratio in Al 0.50 Mn y Co 0.50-y (y=0.36, 0.38, 0.40) alloys affect the magnetic properties. Structural and magnetic investigations by experiments, Thermo-Calc, and ab initio calculations show a dual-phase microstructure containing different fractions of a paramagnetic body-centered cubic (BCC) solid solution and a ferromagnetic B2 phase. The BCC/B2 phase fraction is sensitive to the Al content which strongly affects the saturation magnetization, magnetic transition temperature, and magnetocaloric properties. The magnetocaloric properties of the Al 0.50 Mn 0.38 Co 0.12 alloy show peak values around 430 K with a magnetic entropy change of 0.71 Jkg -1 K -1 , an adiabatic temperature change of 0.40 K, and a refrigeration capacity of 25.56 Jkg -1 under a magnetic field of 650 kAm -1 (0.82 T). These results open new possibilities for identifying promising medium-entropy alloys for magnetocaloric applications. • Al x (Mn 0.76 Co 0.24 ) 1-x (x=0.45, 0.50, 0.55) and Al 0.50 Mn y Co 0.50-y (y=0.36, 0.38, 0.40) alloys were prepared by induction melting. • The analysis indicates that the BCC/B2 phase fraction is more sensitive to the Al content than the Mn/Co ratio • Magnetization and Curie temperature of the alloys have a larger effect from the Al content than the Mn/Co ratio. • The magnetocaloric effect was quantified by measuring the adiabatic temperature change and magnetic entropy change.