Effect of Cu doping on structural and magnetic properties of antiperovskite Mn3Ni(Cu)N thin films

The Mn3Ni(Cu)N thin film with x = 0 at% exhibits antiferromagnetism (AFM) with the Néel temperature as TN = 185 K ((a)). However, as shown in (b-f), the Cu-doping Mn3Ni(Cu)N films with x = 2.3 at%, 5.5 at%, 15.6 at%, 19.2 at%, 35.1 at%, show the same paramagnetic (PM) to ferrimagnetic (FI) transition at TC = 325 K, 323 K, 300 K, 298 K and 284 K, and then followed by an FI to AFM first-order magnetic transition at TN = 166 K, 154 K, 136 K, 133 K and 163 K, respectively. In the case of the Mn3Ni(Cu)N thin film with x = 100 at%, a clear AFM ground state is absent. It appears as if the film shows a PM to FI transition at TC = 237 K ((g)). It is seen that an increase in Cu content weakens the antiferromagnetic interactions while strengthens the ferrimagnetic interactions in the films, resulting in a magnetism transition and decrease in TN.107