Ferromagnetic Mn-implanted GaP: Microstructures vs. magnetic properties

We present a systematic investigation on the evolution of microstructure and magnetic properties as a function of the pulsed laser annealing energy in GaMnP prepared by ion implantation and pulsed laser annealing. The sample microstructure was analyzed by high-resolution X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectrometry (RBS), ultraviolet Raman spectroscopy, and extended X-ray absorption fine structure spectroscopy. The presence of X-ray Pendellösung fringes around GaP (004) and RBS channeling prove the epitaxial structure of the GaMnP layer annealed at the optimized laser energy density (0.40 J/cm2). However, a forbidden TO vibrational mode of GaP appears and increases with annealing energy, suggesting the formation of defective domains inside the layer. These domains mainly appear in the sample surface region and extend to almost the whole layer with increasing annealing energy. The reduction of both the Curie temperature and the uniaxial magnetic anisotropy gradually takes place when more defects and the domains appear along the increasing annealing energy density. This fact univocally points to the decisive role of the pulsed laser annealing parameters on the resulting magnetic characteristics in the processed layers, which eventually determine their magnetic (or spintronics) figure of merit.