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Herein, we report on the potential multifunctional spintronic action of half-metallic graphitic carbon nitride (g-C 4 N 3 ). We observed electrostatic spin-crossover action at an applied electric field of À 0.77 V nm À 1 , which eventually leads to spinswitching action and change in sign of bias dependent spin injection coefficient. The system also acts as a spin polarized charge current rectifier with rectification ratio of 65.41 in spinup channel only. This electric field-controlled spin switching action and simultaneous existence of rectification action makes graphitic carbon nitride a perfect multifunctional spintronic system-an ideal material for quantum logic gate design. Results obtained have been substantiated through transmission spectra and transmission pathways analyses. An analysis of projected device density of states of the system and molecular projected self consistent Hamiltonian states analysis reveals that the electron flow of the system is mainly facilitated by 2p orbitals of C and N atoms.[a] R. . The MPSH states (isovalue: 0.0011 Å), corresponding to the SOHMO of the obtained g-C 4 N 3 system at À 1 V for spin-up (a) and spin-down (b) channel and at + 1 V for spin-up (c) and spin-down (d) channel. 4 5 6 7 8

Herein we present a theoretical foray on crucial role played by the graphitic tunnelling barrier in tuning spintronic feature of two-dimensional insulating graphene layer sandwiched between two ferromagnetic graphitic carbon nitride (g- C4N3) electrodes. We mainly focused on the tuning of spin filter efficiency due to the alteration in tunnelling width. 100% spin filter efficiency reported at each tunnelling width. High degree of spin filter efficiency is restored even at finite bias over a wide range of bias range -1.0 V to +1.0 V. Entire observation have been explained by analysing transmission spectrum at zero bias and a molecular level origin of the observed spintronic response of the device have been provided by analysing the Molecular Projected Self-Consistent Hamiltonian states (MPSH) and transmission pathways of the system.

We report herein existence of a critical tunnelling width beyond which graphitic tunnelling nanostructures exhibit asymmetric spin polarized negative differential resistance feature. Our theoretical foray quite clearly establishes that even with a simple two-dimensional tunnelling nanostructure created by an assembly of ferromagnetic graphitic carbon nitride (g-C4N3) electrodes separated by insulating graphene sheet of variable lengths, there exists a critical tunnelling width at which the system switches from symmetric to asymmetric negative differential resistance feature. Presence of robust spin filer efficiency (100 %) over a wide range of bias variation (À 1.0 to + 1.0 V) added with negative differential resistance action makes the device with shorter tunnelling width of 22.36 Å and 31. 96 Å potentially useful as multifunctional spintronic device. However, at the critical tunnelling width of 36.69 Å and beyond the forward bias negative differential resistance features completely switches off and same is observed only in reverse bias. This switching action certainly opens up the prospect of logic gates operation in quantum circuits. Results obtained has been explained through transmission spectra, transmission pathways and molecular projected self-consistent Hamiltonian states analysis. Emergence of asymmetric IÀ V curve beyond critical tunnelling width has been explained by examining differences in spin injection coefficients.