Magnetoresistance and magnetization of melt-spun Dy-Cu alloys

At low temperatures melt-spun and subsequently annealed ribbons with the nominal composition DyxCu100-x (x < 20) show a remarkable magnetoresistance ratio which is negative and isotropic. This effect is caused by the cubic DyCu5 phase with the AuBe5-type structure. Below a critical temperature T-m approximate to 7K this phase is metamagnetic. Between T-m and T-c approximate to 14.5K it shows a spontaneous magnetization i.e. it is ferromagnetic. The hexagonal DyCu7 phase (TbCu7-type structure) is ferromagnetic with a Curie temperature of about 18K. This 1:7 phase as well as the lamellar Cu/DyCu5 microstructure caused by the eutectoid decomposition of DyCu7 do not result in a large magnetoresistance of the ribbons.