Influence of antiferromagnetic exchange interaction on magnetic properties of ZnMnO thin films grown pseudomorphically on ZnO (0001) single-crystal substrates

This study investigated the influence of antiferromagnetic exchange interaction on magnetic properties of ZnMnO thin films grown on ZnO (0001) single-crystal substrates. Using pulsed laser deposition, ZnMnO films with Mn concentrations as high as 14.1 at. % were prepared. Investigations revealed that the lattice constant along the c axis of the ZnMnO films increases linearly with increasing Mn concentration. The lattice constant along the a axis is independent of the Mn concentration and is equal to that of the ZnO substrate, suggesting pseudomorphic growth of ZnMnO films. An atomic force microscopy image of the ZnMnO film grown at 640 °C shows a step-and-terrace structure. An interference fringe around the ZnMnO 0004 symmetric diffraction image is clearly visible in the 2θ-ω x-ray diffraction profile, suggesting that the samples have a smooth surface and an abrupt interface. The intrinsic magnetic properties of these pseudomorphically grown ZnMnO films with smooth surfaces were evaluated. At temperatures greater than 1.85 K, ZnMnO films with Mn concentration up to 14.1 at. % exhibit typical paramagnetic characteristics. As calculated using the probabilities for a random Mn distribution, the theoretically magnetic moment agreed with the experimentally determined saturated magnetic moment, indicating an antiferromagnetic exchange interaction between the nearest-neighbor Mn ions.