Structural and magnetic properties of antiperovskite Mn₃NiN_x thin films

Influence of nitrogen fractions[N_f=N₂/(N₂+Ar₂)] on the structural and magnetic properties of Mn₃NiN_x thin films prepared on quartz substrates using magnetron sputtering have been studied. The N/Ni ratio increased (N/Ni=0.3-1.1) while the peak (200) shifted to lower angles with increasing N_f. It revealed that there was significant variation in the preferred orientation and Néel temperature (T_N) for the films with increasing N_f. Strong indication for a frozen state is found, determined from the difference between field-cooled and zero-field-cooled magnetizations. The ac susceptibility measurements show a peak position shifting as a function of the driving frequency f and magnetization value does not saturate in the field range. These findings consistently demonstrate that Mn₃NiN_x thin films exhibit a spin-glass state at low temperature.