An Investigation of the Dynamic Susceptibility of Nd(1-x)Sm(x)Co5 Single Crystals and the Effect of Hydrogen absorption.

Measurements are reported on the ac susceptibility of Nd1-xSmxCo5 single crystals, with x 0, 0.25, 0.5, 0.75 and 1.0. The spin reorientation temperature, which occurs at 281K in NdCo5, is found to occur at 167K and approximately 140K in the alloys with x 0.25 and 0.5. Small quantities of absorbed hydrogen raise these temperatures by a few degrees. When a swept biasing field is reversed, the presence of an internal critical field is noted as well as rate dependent losses which cause an apparent drop in the susceptibility. The presence of hydrogen causes a doubling of this field as well as an increase in the losses, which are associated with strong Barkhausen discontinuities. In NdCo5 a strong hydrogen-induced relaxation characterized by an activation energy of 0.4 eV is seen below 220K. Additional relaxations occur near 375K and 720K. Author