Magnetoresistance in Y(Ni_1-xCo_x)₅ around the critical concentration for the onset of ferromagnetism

Resistivity measurements with and without a magnetic field (magnetoresistance) have been used to investigate the pseudobinary Y(Ni_1-xCo_x)₅ system. The aim was to confirm the existence of spin fluctuations mainly at the concentration where the long-range magnetic order appears (x = 0.3) since from the temperature dependence of the susceptibility it has been claimed that YNi₅ is a spin fluctuation system (Coldea et al., J. Magn. Magn. Mat. 157-158 (1996) 627). None of the obtained results indicate that spin fluctuations are significant for the properties, neither for YNi₅ nor for the pseudobinaries around the onset of magnetism.