Fe16N2 thin films possess high saturation magnetization (Ms) and high magnetic crystalline anisotropy (Ku) simultaneously. For application in magnetic recording and electrical machine, soft magnetic materials with high Ms and low Ku are desirable. In this report, carbon was doped into FeN thin films. Fe-CN martensite thin films, also named “Minnealloy,” were fabricated by a facing target sputtering system. The Fe-CN martensite phase was detected by X-ray diffraction (XRD). Vibrating sample magnetometry (VSM) measurements confirmed the high Ms property even though ordered Fe-CN was not formed. An X-ray photoelectron spectroscopy study was carried out to reveal the carbon and nitrogen electronic environment. The Ku value was obtained from the M-H loop and the law to approach saturation with reasonable consistency around 1-2 × 106 erg/cc, which is about five to ten times smaller than that of the ordered Fe16N2 thin film (1-2 × 107 erg/cc). The combination of high Ms and low saturation fields makes the Fe-CN martensite thin film a potential candidate for the magnetic write head and other applications.