Magnetic impurities in graphane with dehydrogenated channels

We have investigated the electronic and magnetic response of a single Fe atom and a pair of interacting Fe atoms placed in patterned dehydrogenated channels in graphane within the framework of density functional theory. We have considered two channels: “armchair” and “zigzag” channels. Fully relaxed calculations have been carried out for three different channel widths. Our calculations reveal that the response to the magnetic impurities is very different for these two channels. We have also shown that one can stabilize magnetic impurities (Fe in the present case) along the channels of bare carbon atoms, giving rise to a magnetic insulator or a spin gapless semiconductor. Our calculations with spin-orbit coupling shows a large in-plane magnetic anisotropy energy for the case of the armchair channel. The magnetic exchange coupling between two Fe atoms placed in the semiconducting channel with an armchair edge is very weakly ferromagnetic whereas a fairly strong ferromagnetic coupling is observed for reasonable separations between Fe atoms in the zigzag-edged metallic channel with the coupling mediated by the bare carbon atoms. The possibility of realizing an ultrathin device with interesting magnetic properties is discussed.

Figure 1

Decoration of hydrogen (a) along diagonal of unit cell leading to an “armchair” channel and (b) along edge of the unit cell leading to “zigzag” channel. In the figure, yellow (light shade in print) balls are bare carbon atoms, turquoise (dark shade in print) balls are hydrogenated carbon atoms and red (small dark in print) balls are H atoms. For both armchair and zigzag channels, the nanoribbons are three rows wide.

Figure 2

Spin-polarized DOS for single Fe atom placed in the three-row “armchair” channel. (a) Total DOS with (blue solid line) and without (red dashed line) Fe. (b) Site– and angular-momentum–projected DOS for six C atoms surrounding the Fe atom. The orange (light gray in print) shaded region shows the $p_z$ component. (c) Site- and angular–momentum-projected DOS for Fe atom ($d$ components only).

Figure 3

Total DOS for five-row and seven-row “armchair” channels with a single Fe impurity.

Figure 4

Spin-density plot of single Fe atom on the three-row “armchair” channel. Red (dark shade in print) is positive spin density and yellow (light shade in print) is negative spin density.

Figure 5

(a)–(c) Spin-polarized DOS for a single Fe atom placed on the three-row “zigzag” channel. (a) Total DOS with (blue solid line) and without (red dashed line) Fe. (b) Site– and angular-momentum–projected DOS for six C atoms surrounding the Fe atom. The orange (light gray in print) shaded region shows the $p_z$ component. (c) Site– and angular-momentum–projected DOS for the Fe atom ($d$ components only). (d) Spin-density plot of a single Fe atom on the three-row “zigzag” channel. Red (dark shade in print) is positive spin density and yellow (light shade in print) is negative spin density.

Figure 6

Spin-polarized total DOS plots for two Fe atoms in the three-row armchair channel. We have plotted the graphs for the range $-3$ to 3 eV to bring out the feature of the DOS near the Fermi level. The numbers in parentheses are the distances between the two Fe atoms.

Figure 7

Spin-density plots. Red (dark shade in print) is positive spin density and yellow (light shade in print) is negative spin density.