Magnetic properties and magnetic-domain structures of nanocrystalline Sm2Fe14.5Cu0.5Ga2Cy

The magnetic properties and magnetic-domain structures of nanocrystalline S m2Fe14.5Cu0.5Ga2Cy (y=0-2.0) alloys prepared by melt spinning and subsequen t heat treatment were studied. The coercivity of optimum annealing ribbons first increases significantly with increasing carbon content for y less tha n or equal to 1.0. It does not change much for 1 < y less than or equal to 2. The maximum coercivity mu(0)H(c) is 2.6 T at room temperature for ribbon s with y=1.5-2.0 after annealing in a Sm atmosphere at 1047 K for 30 min. T he domain structure was studied by magnetic-force microscope. The as-spun a morphous Sm2Fe14.5Cu0.5Ga2C1.5 ribbons exhibit very weak magnetic contrast. The magnetic-domain length scale is 300-700 nm and much larger than the gr ain size in the Sm2Fe14.5Cu0.5Ga2C1.5 ribbons, which may be caused by inter actions between the grains. In the Sm2Fe14.5Cu0.5Ga2 ribbons, the domain-le ngth scale is 100-200 nm and the magnetic-tip-sample interaction strength i s weaker than in the Sm2Fe14.5Cu0.5Ga2C1.5 ribbons. These results have been correlated with the magnetic properties and microstructure. (C) 1999 Ameri can Institute of Physics. [S0003-6951(99)00427-1].