Influence of the L21 ordering degree on the magnetic properties of Co2MnSi Heusler films

We report on the influence of the improved L2(1) ordering degree on the magnetic properties of Co2MnSi Heusler films. Different fractions of the L2(1) phase are obtained by different postgrowth annealing temperatures ranging from 350 degrees C to 500 degrees C. Room temperature magneto-optical Kerr effect measurements reveal an increase of the coercivity at an intermediate annealing temperature of 425 degrees C. This is probably a result of an increasing number of pinning centers on the one hand and a drop of the cubic anisotropy constant K-1 by a factor of 10 on the other for an increasing amount of the L2(1) phase. Furthermore, Brillouin light scattering studies show that the improvement of the L2(1) order in the Co2MnSi films is correlated with a decrease of the saturation magnetization by about 7%. The exchange stiffness constant of Co2MnSi, however, increases by about 8% when the L2(1) order is improved. (C) 2008 American Institute of Physics.