STRUCTURE AND LOCAL MAGNETIC-ANISOTROPY OF MBE-GROWN CO FILMS

Co films of 1000-angstrom thickness's were grown by molecular-beam epi taxy on substrates of mica, oxidized silicon, and glass at temperature s between -33-degrees-C and 800-degrees-C. X-ray diffraction and nucle ar magnetic resonance were used to study the structural quality and ph ase composition as a function of growth temperature and type of substr ate. The magnetic anisotropy of the films was measured using vibrating -sample magnetometry. The film quality is observed to improve sharply for growth temperatures above 200-degrees-C. Below this temperature th e films have a strong polycrystalline character. Above this temperatur e the films on mica and oxidized silicon show well defined (111)/(00.2 ) texture and coherence lengths on the order of the film thickness. Th e structural phase composition depends on both substrate and growth te mperature. For growth on mica at about 500-degrees-C an almost single phased hcp Co film was obtained. Above this temperature the fcc phase dominates the structure, whereas below this temperature stacking fault s dominate. For the films grown on oxidized silicon the structure is d ominated by stacking faults and the fcc phase over the whole growth te mperature range. The overall magnetic anisotropy of the films strongly depends on the structural phase composition. Its magnitude can be sat isfactorily described by a compositional average of the respective bul k anisotropies.