Magnetoresistance of Gd(Al_1-xCu_x)₂

Abstract

The magnetoresistance Δ ρ of the pseudobinary Gd(Al 1- x Cu x ) 2 system was measured up to 15 kOe at several temperatures around the Curie point. The decrease of Δ ρ with increasing magnetic field is explainable on the molecular field theory of s-f exchange interactions. The exchange constant between 4f electrons and conduction electrons estimated from the experimental results varies remarkably with the Cu content x and agrees with that estimated from our earlier resistivity measurements without magnetic field. The importance of the concept of multi-wave expansion of the exchange constant is again stressed as was inferred from our earlier measurements. At the same time, a crucial change in the conduction band structure is suggested to take place with the increase of x . The band structures in ferromagnetic and paramagnetic states are also discussed.