Shock compaction of SmCo5 particles

Fine ferromagnetic particles (1–10 μm) of SmCo5 were compacted using shock pressures of 1.7–27 GPa (17–270 kbar). One-piece disks were produced with pressures in the range 2–9 GPa. X-ray-diffraction measurements revealed no changes in the composition of the compacted SmCo5 for shock pressures below 15 GPa. Magnetic properties of the shocked samples were measured with a superconducting quantum interference magnetometer. In the pressure range 2–9 GPa, the shocked specimens exhibit high intrinsic coercivity Hci. Below 2 GPa, lower values of coercivity were observed, presumably caused by incomplete bonding of particles. Above 10 GPa the intrinsic coercivity drops suddenly and levels off at higher pressures. The remnant magnetization Br, exhibits a broad peak at 6 GPa and then falls off rapidly at higher pressures. The saturation magnetization Ms, has a peak near 10 GPa that correlates with the drop in coercivity. The hardness coefficient a, derived from a fit of the phenomenological ‘‘law of approach’’ formula to the hysteresis curve, shows a linear increase with pressure near 8 GPa. This suggests an increase of inclusions in the samples and correlates with the drop in Hci and the peak in Ms. There is a non-negligible linear contribution to the magnetization given by κH. The nonzero value of κ suggests the possibility of incomplete saturation or paramagnetic impurities. Maximum values in coercivity Hci, remnant magnetization Br, and saturation magnetization Ms are found at about 9 GPa.