| Summary: | Electronic and magnetic properties of Ga<sub>14</sub>N<sub>16−n</sub>Gd<sub>2</sub>C<sub>n</sub> monolayers are investigated by means of the first principle calculation. The generalized gradient approximation (GGA) of the density functional theory with the on-site Coulomb energy U was considered (GGA + U). It is found that the total magnetic moment of a Ga<sub>14</sub>N<sub>16</sub>Gd<sub>2</sub> monolayer is 14 <inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub></mrow></semantics></math></inline-formula> with an antiferromagnetic (AFM) phase. C atom substitutional impurity can effectively change the magnetic state of Ga<sub>14</sub>N<sub>16−n</sub>Gd<sub>2</sub>C<sub>n</sub> monolayers to ferromagnetic phases (FM), and the magnetic moment increases by 1<inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi>μ</mi></mrow><mrow><mi>B</mi></mrow></msub></mrow></semantics></math></inline-formula>/1C. The stable FM phase is due to the p-d coupling orbitals between the C-2p and Gd-5d states. Moreover, Curie temperature (T<sub>C</sub>) close to room temperature (T<sub>R</sub>, 300 K) is observed in the Ga<sub>14</sub>N<sub>16</sub>Gd<sub>2</sub>C<sub>2</sub> monolayer, and the highest value can reach 261.46 K. In addition, the strain effect has a significant positive effect on the <inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi mathvariant="normal">T</mi></mrow><mrow><mi mathvariant="normal">C</mi></mrow></msub></mrow></semantics></math></inline-formula> of the Ga<sub>14</sub>N<sub>16−n</sub>Gd<sub>2</sub>C<sub>n</sub> monolayer, which is much higher than the <inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi mathvariant="normal">T</mi></mrow><mrow><mi mathvariant="normal">R</mi></mrow></msub></mrow></semantics></math></inline-formula>, and the highest value is 525.50 K. This provides an opportunity to further explore the application of two-dimensional magnetic materials in spintronic devices.
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