Exchange Anisotropy in Stainless Steel

“Nonmagnetic” stainless steel is a paramagnetic material at room temperature with a face-centered cubic lattice structure. It has been shown by Kondorsky and Sedov that the susceptibility has an anomaly at 40°K which is quite characteristic of an antiferromagnetic transition. This result suggested to us that cold working such a material to transform part of the material to the ferromagnetic body-centered cubic structure might yield a shifted hysteresis loop, if the bcc structure is in exchange contact with the fcc material. A cold-worked (swaged) type 347 stainless steel did develop a shifted hysteresis loop when cooled in a magnetic field from room temperature to 4.2°K, while the hysteresis loop was symmetrical when the materialwas cooled in a zero magnetic field. We also measured the shift of the hysteresis loop as a function of temperature and found that the shift disappeared at 40°K, which is in agreement with the susceptibility measurements of Kondorsky and Sedov.