Spin-wave measurements on hexagonal MnTe of NiAs-type structure by inelastic neutron scattering

MnTe with a hexagonal structure of NiAs type is an antiferromagnetic semiconductor below the Neel temperature T-N=310 K. The spin-wave excitations of a MnTe single crystal have been measured at T=11 K by inelastic neutron scattering. The experimental spin-wave dispersions, obtained along five high-symmetry directions of the reciprocal space, have been modeled with a Heisenberg Hamiltonian including isotropic exchanges up to the third nearest neighbors and a planar magnetic anisotropy. This yielded the exchange integral values J(1)=-21.5 K, J(2)=0.67 K, and J(3)=-2.87 K. These results are presented and compared to experimental values of relevant diluted magnetic semiconductors, allowing a discussion on a generic description of the distance dependence of the nearest-neighbor magnetic interactions.