Light and electric field control of ferromagnetism in magnetic quantum structures

A strong influence of illumination and electric bias on the Curie temperature and saturation value of the magnetization is demonstrated for semiconductor structures containing a modulation-doped p-type Cd0.96Mn0.04Te quantum well placed in various built-in electric fields. It is shown that both light beam and bias voltage generate an isothermal and reversible cross-over between the paramagnetic and ferromagnetic phases, in the way that is predetermined by the structure design. The observed behavior is in quantitative agreement with the expectations for systems, in which ferromagnetic interactions are mediated by the weakly disordered two-dimensional hole liquid.Comment: 4 pages and 3 figure

Risk factors for pre-term birth in Iraq: a case-control study

BACKGROUND: Preterm birth (PTB)is a major clinical problem associated with perinatal mortality and morbidity. The aim of the present study is to identify risk factors associated with PTB in Mosul, Iraq. METHODS: A case-control study was conducted in Mosul, Iraq, from 1(st )September, 2003 to 28(th )February, 2004. RESULTS: A total of 200 cases of PTB and 200 controls of full-term births were screened and enrolled in the study. Forward logistic regression analysis was used in the analysis. Several significant risk associations between PTB and the following risk factors were identified: poor diet (OR = 4.33), heavy manual work (OR = 1.70), caring for domestic animals (OR = 5.06), urinary tract infection (OR = 2.85), anxiety (OR = 2.16), cervical incompetence (OR = 4.74), multiple pregnancies (OR = 7.51), direct trauma to abdomen (OR = 3.76) and abortion (OR = 6.36). CONCLUSION: The main determinants of PTB in Iraq were low socio-economic status and factors associated with it, such as heavy manual work and caring for domestic animals, in addition to urinary tract infections and poor obstetric history

Two dimensional excitonic magnetic polarons in Cd1-xMnxTe/Cd1-yMnyTe quantum wells

We report an optical study of the excitonic magnetic polaron in Cdl-xMnxTe/Cd1-yMnyTe quantum well. The polaron energy is measured as the Stokes shift observed when the luminescence is selectively excited in the low energy part of the elhl exciton density of states. For quantum wells with a Mn concentration as small as x=0.07 the polaron energy decreases rapidly as the quantum well width increases. This dependence which is consistent with the non-observation of the magnetic polaron in bulk material is well accounted for by a simple theory which assumes a weak initial localisation of the exciton. The mobility edge separating localised and delocalised exciton states is found experimentally to be very close to the maximum of the density of states. For quantum wells with higher Mn concentrations (x=0.14) the polaron energy decrease with increasing well width is much more gradual and the polaron is also observed for excitation on the high energy side of the density of states. This implies a stronger localisation of the heavy hole by alloy fluctuations in this case

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

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. (C) 2000 Elsevier Science B.V. All rights reserved