High field measurements of giant intrinsic magnetic hardness in SmCo/sub 5-x/Ni/sub x/ and SmCo/sub 5-y/Cu/sub y/

The phenomenon of giant intrinsic magnetic hardness in SmCo/sub 5-x/Ni/sub x/ and SmCo/sub 5-y/Cu/sub y/ is investigated in applied fields up to 23.5 T. At 4.2 K, the average propagation field (approximate coercive field) H/sub p/ is approx. =13.0 T, 22.0 T and 18.2 T for x=3, 3.6 and 4.2 respectively, and H/sub p/ is approx. =12.0 and approx. =23.0 T for y=2.5 and 3.6 respectively. At 77 K, values of H/sub p/approx. =5.0 and approx. =5.5 T for y=2.5. Some values of H/sub p/ at 4.2 K are the largest observed to date for any material. The results are consistent with models for thermally activated domain wall motion. For several materials the irreversible portion of the magnetization is not saturated at 23 T and 4.2 K. In these cases the maximum magnetization is less than that observed at 77 K