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We have studied the consequence of structure on the magnetic properties of 304 stainless steel in two distinct crystalline states. Ordinary 304 stainless steel has an fcc structure and is nonmagnetic at room temperature. By using a vapor quenching method, we have fabricated single-phase metastable bcc 304 stainless steel which is strongly ferromagnetic. Films a few µm thick have been made by high-rate sputter deposition onto substrates at room temperature or liquid-nitrogen temperature. Vibrating sample magnetometry and 57Fe Mössbauer spectroscopy reveal that the bcc phase has a magnetization of 130 emu/g, due largely to the Fe moment. The Curie temperature is found to be excess of 550 °C. Upon subsequent annealing above 550 °C, the metastable bcc state transforms back into the usual nonmagnetic fcc phase. The changes in the magnetic properties and the structure of these films during the transformation are examined.