Magneto‐Structural Properties of Multielement Ni–Cu–Co–Mn–Sn Heusler Bulk Alloys

The effect of Cu substitution for Ni on the structural and magnetocaloric properties in Ni 44− x Cu x Co 6 Mn 39 Sn 11 ( x  = 0–4 at.%) bulk Heusler alloys is studied. It is reported that Cu addition stabilizes austenite phase. Generally, martensitic transformation temperature decreases with an increase of Cu concentration up to 4 at.%. The addition of 1 and 2 at.% of Cu allows to shift the temperature of martensitic transformation close to room temperature, while the strong inverse magnetocaloric effect is observed in alloys containing 0–3 at.% of Cu. The value of magnetic entropy at low magnetic field of 15 kOe evolves from 6.3 J kg −1  K −1 for Cu0 to 9.7 J kg −1  K −1 for Cu1, 7.1 J kg −1  K −1 for Cu2, 8.6 J kg −1  K −1 for Cu3, and 4.1 J kg −1  K −1 for Cu4 alloys. The estimated value of the effective refrigerant capacity, including hysteresis loss, is equal to 74.1, 80.4, 106.5, 42.6, and 77.6 J kg −1 for Cu0, Cu1, Cu2, Cu3, and Cu4, respectively.