Alternating current susceptibility study of Dy2Fe17-xGax compounds

The effect of Ga substitution for Fe in Dy2Fe17-xGax on the low field ac su sceptibility is reported. The easy magnetization direction is along the c a xis for x> 6.3 while for x< 6 it is within the basal plane. With decreasing temperature a spin reorientation from an easy axis to an easy cone takes p lace when 6 less than or equal to x less than or equal to 6.3. Two other an omalies have been found in the susceptibility of easy plane materials when the field is applied in the plane: (i) at T near room temperature, both chi ' and chi " depend on the frequency and chi " shows a maximum which shifts to higher temperatures with increasing frequency; (ii) at low temperatures an increase in chi' is accompanied by time varying effects. While the latte r is related to the domain structure reconstruction due to a change of the in-plane anisotropy, the former is caused by thermally activated domain wal l pinning and depinning. The Ga substitution strongly affects the low tempe rature anomaly which disappears when x>2, whereas it has little effect on t he high temperature one. (C) 1998 American Institute of Physics. [s0021-897 9(98)30011-0].