Evidence of ferrimagnetism in Fe₃GaTe₂ via neutron diffraction studies

The van der Waals material Fe₃GaTe₂ is known to exhibit long-range ferromagnetism above room temperature, making it highly attractive for potential two-dimensional spintronic applications. Using a combination of single crystal X-ray diffraction, powder X-ray diffraction, and neutron diffraction, were port that Fe₃GaTe₂ is best described as a self-intercalated ferrimagnet with interstitial iron sites that stabilize its long-range magnetic order at high temperatures. We find the amount of interstitial sites to vary between 7% and 11%, and its total moment to be approximately 1.6(6)μB at 1.5 K by neutron diffraction analysis; the other two iron sites have total moments of 0.7(2)μB and 1.65(6)μB at basetemperature. Group theory analysis reveals that only one magnetic space group is consistent as themaximal isomorphic subgroup of the parent paramagnetic group P6₃/mmc. The resulting magnetic space group of P6₃/mm0c0 leads to a collinear antiferromagnetic arrangement of the interstitial iron sites with respect to those in the telluride layers and with the iron moments all out of plane. Through DFT studies based on the experimental crystal structure, we find that the ferrimagnetic state is favorable over that of the ferromagnetic state by 66 meV. The calculated band structures for the ferromagnetic and ferrimagnetic models show that a significant re-distribution of the electronic density of states occurs near the Fermi level due to the presence of the antiferromagnetically coupled interstitial iron.