Brillouin light scattering from spin waves in Co100−xCrx alloy films

Abstract Collective spin waves in Co100−xCrx alloy films (x=0, 9.2, 15.7 and 35.2 in at%) of 300±5 A in thickness have been studied by means of Brillouin light scattering (BLS) at room temperature in magnetic fields of up to 4.0 kOe. Except for the Co64.8Cr35.2 film, we observed scattering from spin waves and determined the spin wave stiffness constant DB. We obtained a value of DB=(3.47±0.35)×10−9 Oe cm2 (436±44 meV A2) for pure Co. Although this value is in good agreement with recent BLS values, it is rather smaller than the value of 510 meV A2 obtained from neutron scattering. For the alloys, the DB value at x=15.7 is strongly reduced to ∼1/4 of the value at x=9.2, while the saturation magnetization decreases almost linearly as the Cr content increases. We discuss this DB behavior in terms of the Cr segregation which takes a place for Cr contents above x∼12.