To understand the spin-polarized transport properties of ZGNRs, we first investigated the electronic and magnetic properties of ZGNRs. To find the magnetic ground state of ZGNRs, we first optimized the unit cell in the antiferromagnetic (AFM) and ferromagnetic (FM) states. Thereafter, the computed energy difference per unit cell and magnetic moments are tabulated in Table . The large negative value of E F M -AF M = 18.18 meV per unit cell for 6ZGNRH means that 6ZGNR has AFM ground state, which is 18.18 meV per unit cell higher than the FM states. Further, M edge = 0.275 µ B for AFM state and M edge = 0.264 µ B for FM state for 6ZGNRH point towards the magnetic nature of 6ZGNRs. This is in good agreement with the previously reported value of E F M -AF M = 13 meV per unit cell and an edge magnetic moment of M edge = 0.26 µ B for AFM ground state of pristine 6ZGNRH using GGA-PBE. Similar to the 6ZGNRH, the AFM ground spin state is preserved for 2ZGNRH, 4ZGNRH, and 12ZGNRH. This is in complete agreement with the prediction of magnetic states of ZGNR by Pisani et al. The density of states of ZGNRs reveals that ZGNRs are small band gap semiconductors with a band gap of 0.83 eV , 0.72 eV , 0.61 eV and 0.40 eV for 2ZGNRH, 4ZGNRH, 6ZGNRH, and 12ZGNRH respectively, which is in good agreement with the previously reported values. Band gap decreases with increasing width of ZGNRs, as shown in Figure . Apart from the decrease in the band gap with increasing width of ZGNRs, the density of states reveals the spin degenerate nature of energy levels resulting in zero magnetic moments. Although the total magnetic moment of ZGNRs is zero, the spin density plots of ZGNRs (shown in Figure ) reveal the magnetic character of ZGNRs. ZGNRs show the ferromagnetic orientation of spin moments along the edge atoms and the anti-ferromagnetic orientation of spin moments between the opposite edges. The average magnetic moment of edge atoms of ZGNRs increases as 0.216 µ B , 0.253 µ B , 0.275 µ B and 0.276 µ B for 2ZGNRH, 4ZGNRH, 6ZGNRH, and 12ZGNRH respectively. Thus, the average edge magnetic moment of edge atoms first increases with width for smaller ZGNRs and becomes constant after 6ZGNRH. It also confirms that the AFM orientation of spin moments between the opposite edges remains preserved with the increasing width of ZGNRs.