Magneto‐optical Faraday effect in II–VI based semimagnetic semiconductor nanocrystals

Abstract

Different physical and chemical methods were used to prepare II-VI based semimagnetic semiconductor nanocrystals. A study of magneto-optical Faraday effect in the nanocrystals revealed its enhancement as compared with bulk crystals. It is explained in framework of increase in the oscillator strength of exciton transitions and to the difference between these strengths in an external magnetic field. It was observed almost linear dependence of the Faraday rotation as function of magnetic field strength for nanocrystals at liquid helium temperature in contrast to the dependence with saturation in bulk case and changes in process of a transition of the semimagnetic nanocrystals from the paramagnetic state to a spin glass state. One of them is the study of semimagnetic semiconductor quantum dots in the form of nanoparticles or nanocrystals embedded in dielectric matrix. The main feature of the bulk semimagnetic semiconductors type of II 1-x Mn x VI is the strong s,p-d spin exchange interaction between the band carriers and the magnetic ions which results in a large Zeeman splitting of the valence and conduction band states, a giant Faraday rotation and the formation of magnetic polarons. It is obvious that when one goes from bulk material to zero-dimensional structures the mentioned magneto-optical phenomena should be modified by strong confinement in all three dimensions. From the point of view of applications it should be noted [1] that the spin states of carrier confined in such zero-dimensional structures could serve as a Q-bit for quantum information processing. The other practical approach [2] is the application of semiconductor nanocrystals doped with a paramagnetic ions as connector material between ferromagnetic metal and semiconductor which could significantly increase spin injection in spintronic devices. These new aspects clearly demonstrate that semimagnetic semiconductor quantum dots open up many possibilities in spin electronics by providing a versitale system for controlling electron spins with many tunable parameters. In this report we present results of magneto-optical studies of II-VI based semimagnetic semiconductor nanocrystals prepared by different physical and chemical techniques.

Optical and magneto-optical diagnostics of polymer/nanoparticles colloidal solutions and composites

“…The synthesis of CdS:Mn nanoparticles was realized in the multicomponent system CdCl 2 -MnCl 2 -Na 2 S-H 2 Osurfactant (or polymer) at room temperature [8][9][10]. The concentrations of salt solutions of CdCl 2 , MnCl 2 , Na 2 S and the pH value were selected with regard to theoretical considerations.…”

Bismuth Sulfide nanoparticle doped optical current sensors with enhanced Verdet constant

“…No efforts were made to evaluate Verdet constant due to the oscillatory nature of the rotation angle. The occurrence of Faraday Effect in borosilicate glasses doped with semi-magnetic semiconductor Cadmium Manganese Telluride (CdMnTe) quantum dots was reported to cause an enhancement of up to 30 times [2]. The preparation of quantum dot doped samples and the study of Faraday rotation at very low temperatures was also discussed.…”