Optical and magnetic properties of MBE-grown manganese sulfide layers

Metastable zinc-blende MnS layers of various thicknesses from 1.8 nm to 8.6 nm have been grown by molecular beam epitaxy on (100) GaAs between ZnSe cladding layers. We studied the dependences of the optical and the magnetic properties on the layer thickness. On the one hand, the non-exponential decay of the Mn internal transition is found to be faster for thicker layer, which is a size effect and not caused by the interfaces. On the other hand, the Néel-temperature is not altered with decreasing layer thickness, but the phase-transition-induced shift of the internal Mn transitions is smaller for thinner MnS layers. This is explained by the dominating influence of Mn ions at the interface, which possess a reduced number of Mn neighbors. SQUID measurements in a weak external magnetic field confirm the optical observations in zero field. However, applying a strong magnetic field reveals the metamagnetic character of these zinc-blende MnS layers. An antiferromagnetic-to- ferromagnetic phase transition is found with increasing external field.