Au4Mn: A localized ferromagnet with strong spin-orbit coupling, long-rangeferromagnetic exchange, and high Curie temperature

Abstract

Metallic Mn-based alloys with a nearest-neighbor Mn-Mn distance greater than 0.4 nm exhibit large, well-localized magnetic moments. Here we investigate the magnetism of tetragonal Au 4 Mn with a Curie temperature of 385 K, where manganese has a spin moment of 4.1 μ B and its orbital moment is quenched. Since 80% of the atoms are gold, the spin-orbit interaction is strong and Au 4 Mn exhibits uniaxial magnetocrystalline anisotropy with surface maze domains at room temperature. The magnetic hardness parameter of 1.0 is sufficient to maintain the magnetization along the c axis for a sample of any shape. Au also reduces the spin moment of Mn through 5 d − 3 d orbital hybridization. An induced moment of 0.05 μ B was found on Au under a pulsed field of 40 T. Density functional theory calculations indicate that the Mn-Mn exchange is mediated by spin-polarized gold 5 d and 6 p electrons. The distance dependence shows that it is ferromagnetic or zero for the first ten shells of Mn neighbors out to 1.041 nm (64 atoms), and very weak and oscillatory thereafter.