Perpendicular nanomagnetic logic based on low anisotropy Co\\Ni multilayer

Abstract

Cobalt\\Nickel multilayers with low perpendicular magnetic anisotropy are optimized for the lowest achievable coercivity while retaining the highest possible total magnetic moment, still supporting single-domain states. This optimization is done to achieve a vital clock-field reduction in nanomagnetic logic devices with perpendicular magnetic anisotropy, enabling highly efficient on-chip field clocking. It is shown that sub 10 mT coercivities are achievable utilizing a Ta2\\Pt1.5[Co0.2\\Ni0.4]x8 stack in combination with precise manipulation of the anisotropy landscape via highly localized Ga+ ion irradiation, in order to control the point of domain-wall nucleation. Statistical data is used to assess the Ga+ ion dose-dependent coercivity and provide a detailed insight into the overall switching-field-distributions. Nanosecond field pulsing is used to assess the time-evolution of the nucleation fields, confirmed to be following the Arrhenius model at least down to pulse lengths of 10 ns, resulting in nucleation fields more than twice as high. The obtained findings are then applied to demonstrate the first pNML logic elements fulfilling the requirements for on-chip clocking schemes.