Dynamic light scattering (DLS), small-angle neutron scattering (SANS), and viscosity studies have been carried out to examine the influence of NaCl and ethanol on the structure of triblock copolymer [(EO)20(PO)70(EO)20] (EO = ethylene oxide; PO = propylene oxide) micelles in aqueous medium. The studies show that while the pure triblock copolymer solutions do not show any significant growth of the micelles on approaching the cloud point, the presence of a small amount of ethanol (5-10%) induces a sphere to rod shape transition of micelles at high temperatures. Interestingly, this ethanol induced sphere to rod transition of micelles can be brought down to room temperature (25 degrees C) with the addition of NaCl. It is also found that NaCl alone cannot induce such sphere to rod transitions and excess ethanol suppresses them by increasing their transition temperature.

The dilute magnetic semiconductor oxides (DMSO) are of current interest because of their potential 'spintronics' applications, where the charge and spin degrees of freedom of electrons are used simultaneously for novel memory and optical device applications. [1,2] In particular, Co doped ZnO has attracted considerable interest. [3] There have been a number of reports about the observance of room temperature ferromagnetism in thin films of Zn 1-x Co x O produced by different techniques. [4][5][6][7] Schwartz et al. [8] also observed ferromagnetism above room temperature in aggregated particles of Co doped ZnO, by heat treating (below 200 o C) colloidal quantum dots of Co doped ZnO. However, most recent works on well-characterized polycrystalline Zn 1-x Co x O samples indicate that they are not ferromagnetic at room temperature, [9][10][11][12][13][14] except for an isolated report by Deka et al.. [15] In general, studies on polycrystalline samples have converged on to a conclusion that robust room temperature ferromagnetism (RTF) is not realizable in Co doped ZnO without additional carrier doping. Sato and Katayama-Yoshida [16] predicted Co doped ZnO would become ferromagnetic in the presence of n-type carriers. This was experimentally demonstrated by Schwartz and Gamelin. [17] They were the first to show the reversible cycling of paramagnetic (P) to ferromagnetic (FM) state in Co doped ZnO spin coated films, produced from colloidal nanocrystals, by introducing and removing interstitial Zn (Zn i ), a native n-type defect of ZnO. Later Spaldine, [18] in a computational study, showed only hole doping promotes RTF in Co doped ZnO. This is in contrast with

Recent reports, that the samples of nominal compositions, La1-xCexMnO3, form single-phase compounds with orthorhombically distorted perovskite structure, are questionable. Our studies on the sample of nominal composition, La0.7Ce0.3MnO3, and careful analysis of the structural data available in the literature, suggest that the above mentioned samples actually form multi-phase mixtures comprising hole doped lanthanum deficient lanthanum manganate phases and cerium oxide (CeO2).

Magnetic properties of manganese-doped ZnSe quantum dots with the size of approximately 3.6 nm are investigated. The amount of Mn in the ZnSe quantum dots has been varied from 0.10% to 1.33%. The doping level in the quantum dots is much less than that used in the precursor. The co-ordination of Mn in the ZnSe lattice has been determined by electron paramagnetic resonance ͑EPR͒. Two different hyperfine couplings 67.3ϫ 10 −4 and 60.9ϫ 10 −4 cm −1 observed in the EPR spectrum imply that Mn atoms occupy two distinct sites; one uncoordinated ͑near the surface͒ and other having a cubic symmetric environment ͑nanocrystal core͒, respectively. Photoluminescence measurements also confirm the incorporation of Mn in ZnSe quantum dots. From the Curie-Weiss behavior of the susceptibility, the effective Mn-Mn antiferromagnetic exchange constant ͑J 1 ͒ has been evaluated. The spin-glass behavior is observed in 1.33% Mn-doped ZnSe quantum dots, at low temperature. Magnetic behavior at a low temperature is discussed.

Co-and Cu-doped ZnO of nominal composition Zn 0.95 Co 0.05 O and Zn 0.94 Co 0.05 Cu 0.01 O were synthesized by a co-precipitation method in organic media. Rietveld refinement of X-ray diffraction data of the samples annealed at 725 K showed that they are single phase without any secondary phases. DC magnetization measurements of samples with Cu co-doping (Zn 0.94 Co 0.05 Cu 0.01 O) as a function of field at room temperature showed a ferromagnetic signature while the samples without Cu co-doping (Zn 0.95 Co 0.05 O) are paramagnetic in nature. Both the samples heated at 1075 K are found to be paramagnetic at room temperature. Resistivity measurements above room temperature clearly showed a semiconducting behavior with a decreased resistivity value for Zn 0.94 Co 0.05 Cu 0.01 O compared to Zn 0.95 Co 0.05 O and ZnO, confirming additional carriers in Zn 0.94 Co 0.05 Cu 0.01 O due to Cu co-doping. Our results are in agreement with a recent computational study that doping additional carriers are necessary for realizing room temperature ferromagnetism in Co-doped ZnO.