Magnetic order in the chemically-substituted frustrated antiferromagnet CsCrF${}_4$

Abstract

The effect of chemical substitution on the ground state of the geometrically frustrated antiferromagnet CsCrF${}_4$ has been investigated through a neutron powder diffraction experiment. Magnetic Fe-substituted CsCr${}_{0.94}$Fe${}_{0.06}$F${}_4$ and nonmagnetic Al-substituted CsCr${}_{0.98}$Al${}_{0.02}$F${}_4$ samples are measured, and magnetic Bragg peaks are clearly observed in both samples. Magnetic structure analysis revealed a 120${}^{\circ }$ structure having a magnetic propagation vector ${\mathbf{k}}_{\mathrm{mag}}=(0,0,1/2)$ in CsCr${}_{0.94}$Fe${}_{0.06}$F${}_4$. For CsCr${}_{0.98}$Al${}_{0.02}$F${}_4$, a quasi-120${}^{\circ }$ structure having ${\mathbf{k}}_{\mathrm{mag}}=(1/2,0,1/2)$ is formed. It is notable that the identified magnetic structure in CsCr${}_{0.94}$Fe${}_{0.06}$F${}_4$ belongs to a different phase of ground states from those in CsCr${}_{0.98}$Al${}_{0.02}$F${}_4$ and the parent CsCrF${}_4$. These results suggest that the Fe-substitution strongly influences the ground state of CsCrF${}_4$.