Magnetovolume effects in metamagnetic itinerant-electron systems and

High-field magnetization and magnetostriction measurements have been performed for typical metamagnetic itinerant-electron systems and with at 4.2 K in pulsed magnetic fields up to 40 T. The substitution of Al or Ga for Co significantly decreases the critical field of the metamagnetic transition. The magnetovolume coupling constant in the paramagnetic state is nearly constant up to about x = 0.05 and then decreases with increasing x . Moreover, the value of is considerably reduced by the metamagnetic transition. The variation of produced by the change of x or the metamagnetic transition is considered to originate from the change of the spin fluctuation spectrum.