Dilution of a polar magnet: Structure and magnetism of Zn-substituted Co2Mo3O8

• DOI: 10.1103/physrevb.106.174421
• Publication Date: 2022-11-18T15:03:08Z
• Authors: L. Prodan; I. Filippova; A. O. Zubtsovskii; S. Shova; S. Widmann; A. A. Tsirlin; I. Kézsmárki; V. Tsurkan
• Keywords: Isostructural; Magnetism; Ferrimagnetism

We report crystal structure, magnetization, and specific heat measurements on single crystals of the hexagonal polar magnet ${\mathrm{Co}}_{2\text{\ensuremath{-}}x}{\mathrm{Zn}}_{x}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ magnetically diluted by replacing Co Zn. In contrast to transformation from antiferromagnetic a ferrimagnetic state observed in isostructural ${\mathrm{Fe}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ upon small Zn doping, robust behavior is preserved Zn-doped ${\mathrm{Co}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$ up $x=0.55$. The N\'eel temperature decreases ${T}_{\mathrm{N}}=40$ K at $x=0$ 23 $x=0.55$, thus extrapolating $x=1.27$ (36% filling) as percolation threshold typical for three-dimensional, highly coordinated network. This indicates strong magnetic couplings beyond honeycomb planes ${\mathrm{Co}}_{2}{\mathrm{Mo}}_{3}{\mathrm{O}}_{8}$. A sharp peak clear cusp susceptibility associated with onset order whereas $x=0.66$ these features are broadened due increased disorder. Interestingly, in-plane lattice parameter, Curie-Weiss temperature, entropy vary $x$ concerted but nonmonotonic manner. These observations can be traced back site-selective substitution. found that low-doping regime ($x<0.2$) ${\mathrm{Zn}}^{2+}$ ions primarily occupy octahedrally sites, although they have preference occupying tetrahedrally sites higher doping levels. Due multiple interlayer exchange paths, dependent coordination ${\mathrm{Co}}^{2+}$ ions, this reflected variation