Temperature dependence of magnetization of amorphous Tm-Co-B alloys; Mean field analysis

Amorphous melt-spun TmxCo70-xB30 ribbons (x = 0, 2, 4, 6 and 8) were produced in an Ar filled chamber using a single-roller technique. With increasing Tm-concentration the saturation magnetization M(s) as well as the Curie temperature T-C decrease but the crystallization temperature T-x increases. T-C varies from 469 K for x = 2 to 209 K for x = 8 and is always well below T,. A spin compensation effect was observed in amorphous Tm8Co62B30 at 8 K. A two-subnetwork mean-field model is employed to analyse the thermomagnetic data. This analysis yields the spin values of each magnetic subnetwork and the effective exchange interaction constants. The net magnetizations for the Co and Tm subnetworks were determined for temperatures from 0 to T-C and x = 6 and 8.