Itinerant A-type Antiferromagnetic Order in Co${}_{0.25}$TaSe${}_2$

Abstract

We present the magnetic behavior and resulting transport properties of TaSe${}_2$ when intercalated by magnetically active cobalt cations. Acting as the layered host, 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 Co${}_{0.25}$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 K and 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) $\hat{I}{¼}_B$ per Co cation. The direction of the moments are 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 Co${}_{0.25}$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.

13 pages, 8 figures