Itinerant A-type antiferromagnetic order in Co1/4TaSe2

We present the magnetic behavior and resulting transport properties of ${\mathrm{TaSe}}_{2}$ when intercalated by magnetically active cobalt cations. Acting as the layered host, ${\mathrm{TaSe}}_{2}$ is a transition metal dichalcogenide (TMD) that adopts the $2H$-polytype. We find through our single crystal and powder diffraction studies that we can prepare the stoichiometry ${\text{Co}}_{1/4}{\text{TaSe}}_{2}$, which crystallizes in the centrosymmetric space group $P{6}_{3}/mmc$. From magnetic susceptibility and x-ray photoelectron spectroscopy measurements, we find a transition consistent with antiferromagnetic order below the temperature ${T}_{N}=173\phantom{\rule{4pt}{0ex}}\mathrm{K}$ and ${\mathrm{Co}}^{2+}$ in the high-spin state. Neutron powder diffraction and specific heat measurements, however, point to a much smaller than anticipated ordered moment in this sample. From the neutron results, the magnetic structure can be described as an $A$-type antiferromagnet with an ordered moment size of 1.35(11) ${\textmu{}}_{B}$ per Co cation. The direction of the moments is all long the $c$ axis, which is consistent with the magnetization and susceptibility studies showing this direction to be the easy axis. Interestingly, we find that a weak and subtle ferromagnetic component appears to exist along the $ab$ plane of the ${\text{Co}}_{1/4}{\text{TaSe}}_{2}$ crystals. We place the results of this work in the context of other magnetic-ion intercalated TMDs, especially those of Ta and Nb.