We present a study of the magnetic properties of the itinerant-electron systems Ni(3)Al and Ni(3)Ga at ambient pressure. In both compounds the magnetization and susceptibility show a non-Fermi liquid form. We test these properties using a mean-field model of enhanced spin fluctuations on the border of ferromagnetism in three dimensions with no adjustable parameters. While Ni(3)Al is found to be explained well by the standard form of such a model, the data on Ni(3)Ga require us to extend the model to take into account the fact that this system lies close to a tri-critical point. We suggest that such a quantum tri-critical point may be a key feature in the understanding of quantum critical systems more generally.
