Intrachain collinear magnetism and interchain magnetic phases in Cr 3 As 3 − K -based materials

We perform a comparative study of the $\mathrm{K}{\mathrm{Cr}}_{3}{\mathrm{As}}_{3}$ and the ${\mathrm{K}}_{2}{\mathrm{Cr}}_{3}{\mathrm{As}}_{3}$ quasi-one-dimensional compounds and show that the strong interplay between the lattice and the spin degrees of freedom promotes a collinear ferrimagnetic ground state within the chains in the presence of intrachain antiferromagnetic couplings. We propose that the interchain antiferromagnetic coupling in $\mathrm{K}{\mathrm{Cr}}_{3}{\mathrm{As}}_{3}$ plays a crucial role in the experimentally observed spin-glass phase with low critical temperature. In the same region of the parameter space, we predict ${\mathrm{K}}_{2}{\mathrm{Cr}}_{3}{\mathrm{As}}_{3}$ to be nonmagnetic but on the verge of magnetism, sustaining interchain ferromagnetic spin fluctuations while the intrachain spin fluctuations are antiferromagnetic.