First single crystals of a new itinerant antiferromagnet without magnetic elements

Magnetism exists on a spectrum spanning the local to itinerant limit. Theory in the local moment extreme is experimentally confirmed in many magnetic insulators where the magnetism originates from unfilled electronic shells. However, in the itinerant limit, where magnetism stems from band effects, experiment lags theory as there are only three known purely itinerant magnets: ZrZn₂ and Sc_3.1In, both FM, and TiAu an AFM. While ZrZn₂ has been made in single crystal form, no single crystals have been made of a purely itinerant AFM, until now. We present the results on single crystals of a new itinerant AFM with no magnetic constituent elements which orders at T_N= 11 K. The paramagnetic moment is large, 1.0 μ_B/FU, compared to the saturated moment of 0.25 μ_B/FU, leading to a Rhodes-Wohlfarth ratio of 4. The entropy release is small, just 0.7%Rln2, yet muon spin relaxation measurements confirm the order is intrinsic. DFT calculations confirm the small moment and conclude a Fermi surface nesting mechanism is responsible for the magnetic order. Having the first purely itinerant AFM crystal paves the way for advance experiments that will allow a fundamental understanding of this class of materials for the first time.