Optical response of a ferromagnetic-diluted magnetic semiconductor hybrid structure

Abstract

We investigate the possibility of using local magnetic fields to produce one-dimensional traps in hybrid structures for any quasiparticle possessing spin degree of freedom. We consider a system composed of a diluted magnetic semiconductor quantum well buried below a micron-sized ferromagnetic island. Localized magnetic field is produced by a rectangular ferromagnet in close proximity of a single domain phase. We make quantitative predictions for the optical response of the system as a function of distance between the micromagnet and the quantum well, electronic g-factor, and thickness of the micromagnet.The use of the spin of quasi-particles, instead of their charge, as a basis for the operation of a new type of electronic devices has attracted the attention of a large interdisciplinary research community. The interest is not only in the phenomenology but also in the large scale production and applicability of such devices [1]. In this paper we show that the spin degree of freedom can be utilized for achieving spatial localization of charged quasiparticles such as electrons, holes or trions [2,3], as well as of neutral complexes such as excitons [4,5]. This is of interest for spintronic applications. In diluted magnetic semiconductors (DMS) like CdMnTe, due to the exchange interaction between delocalized band electrons and localized magnetic ions, the presence of a static magnetic field leads to a giant Zeeman splitting between band states for different spin components. As a consequence, the effective g-factor for the DMS is very high and temperature dependent [6,7].Here we consider a hybrid structure of a CdMnTe/CdMgTe quantum well (QW) at tens of nanometers below a rectangular ferromagnetic island. We find that due to the giant Zeeman interaction, the non-homogeneous magnetic field produced by the rectangular ferromagnetic island acts as an effective potential that can efficiently "trap" spin polarized quasi-particles in the QW. We present quantitative predictions for the optical response of the DMS where the localization of the quasi-particles is evident. We also discuss how these predictions are sensitive to the variation of certain parameters, such as the distance between the QW and the ferromagnetic island, the thickness of the micromagnet, and the electronic g-factors (g e -g-factor of the electron, g h -g-factor of the hole).We consider a typical rectangular micromagnet (iron) of dimensions D x =6 µm, D y =2 µm and D z =0.15 µm in a single domain state [8], with magnetization pointing in the x-direction [9, 10, 11], see Fig. 1. The single * Electronic address: Pawel.Redlinski.1@nd.edu domain state of the micromagnet was investigated with micro-magnetic simulation using the OOMMF package made available by NIST [12]. In the absence of an external magnetic field the micromagnet has a multi-domain structure. The simulation shows that after magnetizing the sample with a field of 1 T and then reducing the field to 0 T, a value of 0.2 T is enough to restore a state that is, for our purposes, sufficiently close ...

Calculation of band offsets in Cd1−xXxTe alloys, X=Zn, Mg, Hg and Mn and magnetic effects in CdMnTe

“…We note that our calculated valence band offsets for CdTe/MgTe (0.75 eV), CdTe/Cd 0.65 Mg 0.35 Te (0.26 eV) agree with those given in Refs. [37] and [38] respectively. Note that this later is given for …”

Magnetism in melt grown dilute magnetic semiconductor Ge1−xMnx from electron density

“…Resistivity measurements have also been done in DMS Ge 1 À x Mn x showing metal-insulator transition down to 18 K [5]. Fabrication and characterization of bulk and thin films of Mn-doped Ge DMS with various doping levels of Mn have been carried out by researchers [4][5][6][7][8][9]. Electrical and magnetic properties have been extensively studied in these Ge based DMS materials.…”

“…Good quality single crystals of Ge 1À x Mn x (0oxo0.1) were grown using Bridgman's crystal growth technique and studied by Kang et al [14]. These works [4][5][6][7][8][9][10][11][12][13][14] reveal the fact that the preparation of homogeneous Ge 1À x Mn x DMS samples is very difficult and it was found that strong phase separation exists with dominant phases such as Mn-poor Ge 8 Mn 11 and Mn-rich Ge 3 Mn 5 . Beigger et al [15] compared the magnetic data of Ge 1 À x Mn x with other phases like Ge 8 Mn 11 and Ge 3 Mn 5 and observed that there was a strong ferromagnetic behavior in Ge 1À x Mn x which arises mainly due to phase separated Mn-rich domain Ge 3 Mn 5 .…”

“…The room temperature FM DMSs discovered in experiments [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] pose challenge to theoretical work because the origin of ferromagnetism in these materials is still an open question. First principle calculations on Mn-doped Ge made by Park et al [3] indicate that the FM order arises from a long range FM interaction competing with a short range AFM one.…”

Growth of novel-diluted magnetic semiconducting material Ge1−xMnx and X-ray characterization by the maximum entropy method (MEM) and pair distribution function (PDF)

“…This is a challenge because most magnetic semiconductors lose their magnetic properties at temperatures near room temperature and would require expensive and impractical refrigeration in order to work in actual computer. These developments have induced researchers to grow and characterize some of the DMS materials using both forms single crystals and thin films [3][4][5][6].…”