II-VI and II1-xMnxVI semiconductor nanocrystals formed by the pressure cycle method

II-VI and II1-xMnxVI nanocrystals were prepared by the pressure cycle method using the Paris-Edinburgh cell. The recovered samples are nanocrystals in the cubic phase zinc-blend (ZB) structure and were characterized using transmission electron microscopy, electron diffraction, X-ray diffraction and Raman scattering. Transmission electron micrographs show that these nanocrystals are nearly spherical with diameters ranging from 20 to 50 nm depending on the sample under investigation. The Raman scattering measurements confirm the existence of II-VI nanocrystals in the cubic phase (ZB). The magnetic properties of Cd0.5Mn0.5Te nanoparticles were found to vary with the particle size and were different from those observed for the Cd0.5Mn0.5Te bulk initial samples. The X vs. T data show temperature hysteresis due to spin-glass form, which occurs at T-g = 21 K, for both the bulk as well as for the recovered nanoparticle samples. The zero-field cooled and field-cooled X vs. T curves for the nanoparticles showed a monotonous increase below Tg. Below similar to 21 K, the M vs. B curve for the recovered nanoparticle samples exhibited magnetic hysteresis, and this is attributed to a weak ferromagnetic contribution. This contribution is also observed in the chi(T) curves and is due to a large surface/volume ratio of the nanoparticles, which enhances the magnetic interaction.