It was recalled that previous results had indicated that neutron irradiation was an effective method for improving the pinning strength and critical current density of this material. This demonstrated that Hg-based materials were not intrinsically limited to low current densities. Further investigations were made here of random powders by studying the effects of neutron irradiation and annealing upon the magnetization hysteresis and flux creep of powder samples. A study was also made of the effects of irradiation upon aligned powder samples in order to clarify the relationship between flux pinning and magnetic anisotropy. It was found that the critical current density continued to increase with increasing neutron fluence, but at a decreasing rate. The irradiation enhancement in ground, and subsequently aligned, powders was not as large as in the case of as-sintered material. This was attributed to the effect of small defects which were introduced during the grinding process and inhibited the formation of defect clusters during irradiation. It was also found that the neutron irradiation decreased and inverted the anisotropy, as measured by magnetization hysteresis.

K.M.Amm, J.Schwartz: Journal of Applied Physics, 1995, 78[4], 2575-80