Spin density waves in periodically strained graphene nanoribbons.

Zigzag graphene nanoribbons (ZGNRs) are antiferromagnetic in the ground state with zero net magnetization due to the compensation of contributions from opposite edges. Uniform deformations (both shear and axial) do not produce magnetization due to symmetry restrictions. However, we report the results of first-principles calculations that predict the induction of spin density waves (SDWs) in ZGNRs under non-uniform periodic strain. Using the density functional theory (DFT) method, we show that a sinusoidal magnetization variation along the axis of the ribbon occurs under a sinusoidal transversal shear strain. SDWs appear due to the presence of a strain gradient that induced asymmetry of magnetization on opposite edges of ZGNRs which do not compensate each other. The amplitude of SDWs is estimated at ∼0.066 μB when deformations transverse to the ZGNR axis have a sinusoidal profile with a period of 88.6 Å and an amplitude of 1 Å. Our study suggests that the periodic lattice deformations strongly affect the magnetic structure of ZGNRs in the case of acoustic phonons or mechanical waves.