Amorphous Fe40Ni40B20 alloy is treated with infrared heat pulses in the presence of a dc field to facilitate the relaxation of the internal stress. Magnetic properties like initial susceptibility, magnetization, remanence, magnetostriction and effective anisotropy are measured in as-received and heat treated samples. Magnetic softness increases when treated with short duration heat pulses. The stress dependence of the above properties have been studied. It is found that the normal curves of as-received and heat treated samples under different stresses reduce to the single curve when expressed in terms of reduced variables M/MD vs. H/Hc, where MD and Hc are the domain saturation magnetization and coercive field, respectively. The results are consistent with the model due to Vazquez et al. © 1988.