Magneto-optical properties of semimagnetic lead chalcogenides

Abstract

Magneto-optical properties of PbTe and PbSe alloyed with paramagnetic ions Mn and Eu are reviewed. The k . p theory of the band structure of IV-VI compounds is presented, taking into account the narrow energy gaps and strong spin-orbit interactions in the materials. The exchange interaction between the paramagnetic ions and mobile carriers is included in the framework of the meanfield approximation. The experimental data of various authors on magnetization, interband magneto-optics. intraband magneto-optics and four-wave mixing are presented. All results are successfully described by the theory, treating the exchange integrals as adjustable parameters. It is shown that the exchange interaction is of particular importance for the valence bands. Differences between semimagnetic behaviours of Mn-based and Eu-based systems are emphasized as well as those between the IV-VI and Il-VI semimagnetic compounds.

Optical second harmonic generation in the centrosymmetric magnetic semiconductors EuTe and EuSe

“…[66][67][68][69][70][71][72][73] The lowest-energy conduction band has a narrow width of ϳ100 meV, 61,62 so that it can be described by a tight-binding model. The basis set of the tight-binding wave functions consists of the 5d orbitals of the Eu atoms, split by the octahedral crystal field into a twofold degenerate lowenergy 5d͑t 2g ͒ state, and a 5d͑e g ͒ state at about 2 eV higher energy.…”

“…This assertion is consistent with magneto-optical data. [66][67][68][69][70][71][72][73] It is also generally assumed that a broad conduction band with 6s character is nearly resonant with the 5d͑t 2g ͒ states, however, electric-dipole coupling of the 4f 7 ͑ 8 S 7/2 ͒ state to this 6s band is forbidden, which is therefore optically dark. The single-particle electronic structure in EuTe is shown schematically in Fig.…”

IV-VI Semimagnetic Semiconductors: Recent Developments

“…These, for example, are the carrier concentration induced paramagnet-ferromagnet and ferromagnet-spin glass transitions [1,2], and large temperature and magnetic field dependent spin splittings of band states [3]. The specific properties f IV-VI matrices make the IV-VI semimagnetic semiconductors a particularly interesting object f research.…”

“…They show, in particular, semimetallic electric properties and allow for a simple control of carrier concentration by means f doping or isothermal annealing. As opposed to II-VI semimagnetic materials, IV-VI crystals are known to form solid solutions not only with magnetic ions from 3d group (like Mn), but also with the elements f 4f group (Eu, Gd, Ce, Yb) [3][4][5] and the elements f 5 f group (U) [6].…”

Diluted Ferromagnetic Semiconductors—Theoretical Aspects

“…Since, in contrast to magnetic semiconductors, neither narrow magnetic bands nor long-range magnetic ordering affected low-energy excitations, DMS were named semimagnetic semiconductors. More recently, research on DMS have been extended toward materials containing magnetic elements other than Mn as well as to III-VI, IV-VI (Bauer, Pascher and Zawadzki, 1992), and III-V compounds as well as group IV elemental semiconductors and various oxides (Prellier, Fouchet and Mercey, 2003). In consequence, a variety of novel phenomena had been discovered, including effects associated with narrow bands and magnetic phase transformations, making the borderline between properties of DMS and magnetic semiconductors more and more elusive.…”