On the magnetic contribution to the inverse magnetocaloric effect in Ni-CoCu-Mn-Sn metamagnetic shape memory alloys

Martensitic transformation and magnetic properties in directionally solidified Ni45-xCoxCu5Mn39 Sn-11 (x = 0, 1, 2) alloys were studied. The martensitic transformation temperature decreases with increasing Co concentration, whereas the Curie temperature of austenite increases, what then alters the magnetic state of austenite at the onset of martensitic phase transformation. Concomitantly the effective magnetic moment of austenite increases by 0.7 with Co substitution. Under an applied magnetic field of 5 T the peak values of the magnetic entropy changes reach 11.4 J/kgK (x = 1) and 4.5 J/kgK (x = 2). The variations in magnetic entropy are discussed in relation to a stronger ferromagnetic contribution promoted by Co in the martensite phase.