Ultrafast spin dynamics in magnetic trimer and tetramer clusters: a step towards prototypic spin-SHIFT registers

Abstract

Ultrafast magnetic dynamics is a necessary ingredient for magnetic recording and ultrafast information processing.
The shift functionality, although not mandatory for Boolean logic, is always implemented in CMOS
CPUs and therefore must be also present in magnetic logic. In this respect, using ab initio calculations we show
ultrafast spin dynamics in molecular clusters such as Co+3 CO and Ni4. In this work, we establish that clusters
with magnetic atoms can provide a theoretical toolbox for efficient spin charge dynamics whose operation time
can range up to a few picoseconds. The prime underlying mechanism for all spin manipulation scenarios in the
above mentioned clusters are laser-induced Λ processes where the laser parameters are fully optimized using a
genetic algorithm. In general, a structural asymmetry enforces substantial spin localization on the active centers
of both the magnetic clusters. Keeping in mind the shift functionality, we theoretically suggest a series of spin
transfer scenarios between the Co and Ni atoms in each of these two clusters independently to construct a 3-bit
and a 4-bit cyclic spin-shift register, respectively. The maximum operational time for both the logic devices are
2 ps, which is much faster than the response time of conventional spintronic devices. Additionally, for a better
understanding of the transfer cycles, their feasibility and reversibility are also investigated through the analysis
of the optical spectra of the related states. Our results provide important theoretical guidance for ultrafast spin
manipulation in molecular structures as well as their potential spin functionality, and thus step closer to the realization
of future spin-based logic devices and quantum computation. This effectively motivates the investigation
and precise establishment of the shift functionality in magnetic trimers and tetramers.