SHOCK COMPACTION OF SMCO5 PARTICLES

Fine ferromagnetic particles (1-10 mu m) of SmCo5 were compacted using shock pressures of 1.7-27 GPa ((71-270 kbar)). One-piece disks were p roduced with pressures in the range 2-9 GPa. X-ray-diffraction measure ments revealed no changes in the composition of the compacted SmCo5 fo r shock pressures below 15 GPa. Magnetic properties of the shocked sam ples were measured with a superconducting quantum interference magneto meter. In the pressure range 2-9 GPa, the shocked specimens exhibit hi gh intrinsic coercivity H-ci. Below 2 GPa, lower values of coercivity were observed, presumably caused by incomplete bonding of particles. A bove 10 GPa the intrinsic coercivity drops suddenly and levels off at higher pressures. The remnant magnetization B-r, exhibits a broad peak at 6 GPa and then falls off rapidly at higher pressures. The saturati on magnetization M(s), has a peak near 10 GPa that correlates with the drop in coercivity. The hardness coefficient alpha, derived from a fi t of the phenomenological ''law of approach'' formula to the hysteresi s curve, shows a linear increase with pressure near 8 GPa. This sugges ts an increase of inclusions in the samples and con-elates with the dr op in H-ci and the peak in M(s). There is a non-negligible linear cont ribution to the magnetization given by kappa H. The nonzero value of k appa suggests the possibility of incomplete saturation or paramagnetic impurities. Maximum values in coercivity H-ci, remnant magnetization B-r, and saturation magnetization M(s) are found at about 9 GPa. (C) 1 996 American Institute of Physics.