Study of magnetic anisotropy in the array of the nanometric semi-spherical calotte

GARCIA FLÁVIO; COUGO MAURICIO; SAMPAIO LIMA LUIS CARLOS; DE BIASI EMILIO

Kyoto, Japan.

Congreso; International Conference on Magnetism; 2006

In a recent work, Albrecht et al. have shown that is possible to tune an out plane arbitrary magnetic anisotropy axis of particular magnetic nano-structure system simply by varying the deposition angle. The system studied by these authors is an auto-organized nano-spheres array capped by a [Co/Pd] multilayer, with a strong perpendicular anisotropy. In the present work, we have carried out a systematic study of the influence of the depositing condition, and the intrinsic anisotropy of the capped film (eg. the anisotropy of the flat film) on the magnetic properties of the auto-organized array of the different sizes latex nano-spheres (50, 200, 500 and 1000 nm). The samples were deposited by dc sputtering machine in two different conditions: the first is with a planetary substrate movement, that stands a well homogeneity of the deposited film; and the second way is in perpendicular deposition. The choused deposited films it were [Co(0.4)/Pd(1nm)]x6 that present a very strong perpendicular anisotropy, [Co(0.8)/Pd(1nm)]x6 that present an insipient perpendicular anisotropy, and Co and Py single layers that present a well defined in plane anisotropy and a isotropic behavior respectively. Theses samples have been analyzed by means of the MOKE, Extraordinary Hall Effect, Scanning Electronic Microscopy, AFM, MFM, SQUID and for to get a better understanding of the micromagnetic behavior of the sping configurations, we performed some simulations. The samples have shown a nice degree auto-organization. From the magnetic characterization, we have observed the increase of the effective perpendicular anisotropy in the samples [Co(0.8)/Pd(1nm)] as well the sphere size decrease. Two regimens were observed, in the greater spheres there are two regions (domains) that contributed to the planar and perpendicular anisotropies characteristics, however the smaller caps shows one defined perpendicular anisotropy behavior. The interpretation of these anomalous behaviors it was based in the vortex formation, originated by the competition of the magnetostatic and exchange interaction in a particular morphology. This interpretation is corroborated by MFM images and the micromagnetics simulations.