Electrical & Computer Engineering Research Works
Permanent URI for this collectionhttp://hdl.handle.net/1903/1658
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Item Spin-stand imaging of overwritten data and its comparison with magnetic force microscopy(American Institute of Physics, 2001-06-01) Mayergoyz, I. D.; Tse, C.; Krafft, C.; Gomez, R. D.A new technique of magnetic imaging on a spin-stand [Mayergoyz et al., J. Appl. Phys. 87, 6824 (2000)] is further developed and extensively tested. The results of successful imaging of digital patterns overwritten with misregistration ranging from 0.3 to 0.07 mm are reported. The results are compared with magnetic force microscopy (MFM) images and the conclusion is reached that the spin-stand imaging technique can provide (at least) the same level of resolution and accuracy as the MFM imaging technique.Item Current-controlled bi-stable domain configurations in Ni81Fe19 elements: An approach to magnetic memory devices(American Institute of Physics, 2002-07-29) Koo, H.; Krafft, C.; Gomez, R. D.The discovery of current-switchable bi-stable remanent domain configurations on small ferromagnetic islands is reported. Rectangular NiFe islands with a thickness of 50 to 100 nm and lateral dimensions on the order of several microns were imaged using magnetic force microscopy after application of 10 ns current pulses through the material. The closure configuration can be set into either the 4 or 7 domain configuration by applying positive or negative current polarity at density on the order 107 A/cm2. The chirality of the closure patterns is fixed, implying that only two rather than four states are stable in these patterns. The possibility of using these configurations as a means of storing a logic state for memory applications is discussed.Item „(Towards) Spin-polarized scanning tunneling microscopy of NiFe films on a chromium„001… single crystal: Growth and electronic structure of Permalloy(American Institute of Physics, 2005-05-10) Dreyer, M.; Lee, J.; Krafft, C.; Gomez, R.This paper shows spin-polarized tunneling on the terraces of antiferromagnetic chromiums001d. Details on the morphological and chemical composition are shown as a function of various stages of surface preparation, and protocols for obtaining Crs001d that reveal spin-polarized contrast are reported. On the clean crystal the chromium surface state at the Fermi level could be observed. The spin splitting of the state was measured by using an iron coated tungsten tip. A spin polarization of 10% was observed. The properties of NiFe grown on Crs001d measured using nonpolarized tunneling spectroscopy are also reported. Monolayer thick permalloy grows in Volmer–Weber mode, exhibiting pyramidal islands oriented along the chromium k110l direction. Spectroscopic data reveal that NiFe alloying is preserved.Item Spin-current-induced magnetization reversal in magnetic nanowires with constrictions(American Institute of Physics, 2005-05-05) Florez, S. H.; Krafft, C.; Gomez, R. D.We have performed experiments on current-induced domain-wall motion sCIDWMd in the case of the domain walls sDWd trapped within the nanoscale constrictions in patterned NiFe structures. Direct observation of current-induced magnetization reversal was achieved and critical current densities jc were measured in the presence of easy-axis magnetic fields. The direction of CIDWM was found to be along the direction of the electron motion in absence of an applied magnetic field and in the direction of the field when in the presence of even relatively weak fields. Data for the field dependence of jc for both uniform and fast rising pulses suggest that the current, regardless of polarity, assists in the depinning of the DW. Only for the dc case does the data strongly reveal the influence of the electron pressure in promoting or hindering DW motion.