a 00 -Fe 16 N 2 thin films have been prepared by facing-target sputtering. Their structures, magnetic properties and thermal stability were studied by X-ray diffraction (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). It was found that the saturation magnetization (M s ) of a 00 -Fe 16 N 2 decreases with increasing temperature, and at about 523 K, a sudden change was observed, which can be attributed to the decomposition of a 00 -Fe 16 N 2 into a-Fe and g 0 -Fe 4 N.