Structural Disorder and Elementary Magnetic Properties of Triangular Lattice ErMgGaO4 Single Crystals

The single crystal growth, structure, and basic magnetic properties of ErMgGaO4 are reported. The structure consists of triangular layers of magnetic ErO6 octahedra separated by a double layer of randomly occupied non-magnetic (Ga,Mg)O5 bipyramids. The Er atoms are positionally disordered. Magnetic measurements parallel and perpendicular to the c axis of a single crystal reveal dominantly antiferromagnetic interactions, with a small degree of magnetic anisotropy. A weighted average of the directional data suggests an antiferromagnetic Curie Weiss temperature of approximately -30 K. Below 10 K the temperature dependences of the inverse susceptibilities in the in-plane and perpendicular-to plane directions are parallel, indicative of an isotropic magnetic moment at low temperatures. No sign of magnetic ordering is observed above 1.8 K, suggesting that ErMgGaO4 is a geometrically frustrated magnet.