Itinerant A-type Antiferromagnetic Order in Co0.25TaSe₂

We present the magnetic behavior and resulting transport properties of TaSe₂ when intercalated by magnetically active cobalt cations. Acting as the layered host, TaSe₂ 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 Co0.25TaSe₂, which crystallizes in the centrosymmetric space group P6₃/mmc. From magnetic susceptibility and x-ray photoelectron spectroscopy measurements, we find a transition consistent with antiferromagnetic order below the temperature TN = 173 K and Co²⁺ 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) μB 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 Co0.25TaSe₂ crystals. We place the results of this work in the context of other magnetic-ion intercalated TMDs, especially those of Ta and Nb.