D. Ferrand

Carrier-induced ferromagnetism in p − Zn 1 − x Mn x Te

We present a systematic study of the ferromagnetic transition induced by the holes in nitrogen doped

Large Magnetoresistance Effect Due to Spin Injection into a Nonmagnetic Semiconductor

{\mathrm{Zn}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Te}

Ordered magnetic phase in Cd1-xMnxTe/Cd1-y-zMgyZnzTe : N heterostructures: magnetooptical studies

epitaxial layers, with particular emphasis on the values of the Curie-Weiss temperature as a function of the carrier and spin concentrations. The data are obtained from thorough analyses of the results of magnetization, magnetoresistance, and spin-dependent Hall effect measurements. The experimental findings compare favorably, without adjustable parameters, with the prediction of the Rudermann-Kittel-Kasuya-Yosida (RKKY) model or its continuous-medium limit, that is, the Zener model, provided that the presence of the competing antiferromagnetic spin-spin superexchange interaction is taken into account, and the complex structure of the valence band is properly incorporated into the calculation of the spin susceptibility of the hole liquid. In general terms, the findings demonstrate how the interplay between the ferromagnetic RKKY interaction, carrier localization, and intrinsic antiferromagnetic superexchange affects the ordering temperature and the saturation value of magnetization in magnetically and electrostatically disordered systems.

Carrier-induced ferromagnetic interactions in p-doped Zn(1−x)MnxTe epilayers

A novel magnetoresistance effect, due to the injection of a spin-polarized electron current from a dilute magnetic into a nonmagnetic semiconductor, is presented. The effect results from the suppression of a spin channel in the nonmagnetic semiconductor and can theoretically yield a positive magnetoresistance of 100%, when the spin flip length in the nonmagnetic semiconductor is sufficiently large. Experimentally, our devices exhibit up to 25% magnetoresistance.

p-type doping of II–VI heterostructures from surface states: Application to ferromagnetic Cd1−xMnxTe quantum wells

Photoluminescence magnetospectroscopy is employed to examine the low-temperature magnetic phase that is induced by the carrier-mediated ferromagnetic exchange interaction in modulation-doped Cd1-xMnxTe quantum well. Unusual properties of the domain structure are linked to tendency towards spin-density wave formation in this low-dimensional magnetic system

Ferromagnetic Ga1 − xMnxN epilayers vs. antiferromagnetic GaMn3N clusters

Abstract p-type doping of molecular-beam-epitaxy grown layers of the diluted magnetic semiconductor Zn(1−x)MnxTe is achieved by using an active nitrogen cell. The strong interaction between the localized Mn spins and the holes deeply modifies the transport properties (metal–insulator transition, spin-dependent Hall effect). In spite of the weak localization of the carriers at low temperature, the holes clearly induce a ferromagnetic interaction between the localized spins, which is discussed as a function of Mn content and hole concentration.

Magneto-optical spectroscopy of (Ga,Mn)N epilayers

We present a study of p-type doping of CdTe and Cd1−xMnxTe quantum wells from surface states. We show that this method is as efficient as usual modulation doping with nitrogen acceptors, and leads to hole densities exceeding 2×1011 cm−2. Surface doping was applied to obtain samples with Cd1−xMnxTe quantum well with up to x=9.3% containing hole gas. We could also increase the growth temperature up to 280 °C, which results in sharper photoluminescence lines, when compared to the similar nitrogen doped samples. Carrier-induced ferromagnetism was observed in surface doped samples.

Ferromagnetism in II–VI Compounds

Mn-doped wurtzite GaN epilayers have been grown by nitrogen plasma-assisted molecular-beam epitaxy. Correlated SIMS, structural and magnetic measurements show that the incorporation of Mn strongly depends on the conditions of the growth. Hysteresis loops which persist at high temperature do not appear to be correlated to the presence of Mn. Samples with up to 2% Mn are purely substitutional Ga1 − xMnxN epilayers, and exhibit paramagnetic properties. At higher Mn contents, precipitates are formed which are identified as GaMn3N clusters by X-ray diffraction and absorption: this induces a decrease of the paramagnetic magnetisation. Samples co-doped with enough Mg exhibit a new feature: a ferromagnetic component is observed up to Tc ~ 175 K, which cannot be related to superparamagnetism of unresolved magnetic precipitates.

Carrier-mediated ferromagnetic interactions in structures of magnetic semiconductors

We report on the magneto-optical spectroscopy and cathodoluminescence of a set of wurtzite (Ga,Mn)N epilayers with a low Mn content, grown by molecular beam epitaxy. The sharpness of the absorption lines associated to the Mn

Optical properties of single ZnTe nanowires grown at low temperature

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