Domain structure of bulk ferromagnetic crystals in applied fields near saturation

We investigate the ground state of a uniaxial ferromagnetic plate with perpendicular easy axis and subject to an applied magnetic field normal to the plate. Our interest is the asymptotic behavior of the energy in macroscopically large samples near the saturation field. We establish the scaling of the critical value of the applied field strength below saturation at which the ground state changes from the uniform to a branched domain magnetization pattern and the leading order scaling behavior of the minimal energy. Furthermore, we derive a reduced sharp-interface energy giving the precise asymptotic behavior of the minimal energy in macroscopically large plates under a physically reasonable assumption of small deviations of the magnetization from the easy axis away from domain walls. On the basis of the reduced energy, and by a formal asymptotic analysis near the transition, we derive the precise asymptotic values of the critical field strength at which non-trivial minimizers (either local or global) emerge. The non-trivial minimal energy scaling is achieved by magnetization patterns consisting of long slender needle-like domains of magnetization opposing the applied fieldComment: 38 pages, 7 figures, submitted to J. Nonlin. Sci

THE FIELD DEPENDENCE OF THE DOMAIN PERIOD IN CoCr FILMS

The dependence of the submicron domain period of CoCr films in ascending and descending fields (dc : 8-320kA/m ; superposed ac : 0-55 kA/m) normal to the surface was investigated using the colloid-SEM method. Low coercivity samples (Hc/Hk ~ 0.02) were measured. Comparison with calculations furnished fair agreement in contradistinction to samples havig Hc/Hk ~ 0.05. The exchange constant A was deterrnined from the thickness dependence of the domain period

Domain observation of a CoCr film by the colloid-sem method

The domain structure of a CoCr film was studied in different magnetic fields using the method of a combination of the colloid technique and scanning electron microscopy (colloid-SEM method). The results obtained are presented and the advantages of this method are discussed