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Magnetic nanogranular materials have shown promising magnetic and electron transport properties, offering key advantages for a range of applications from spintronics components to magnetic field sensors. In this paper, the properties of Co nanoparticles synthesized using low-energy ion implantation and electron beam annealing (EBA) on SiO2were investigated. EBA leads to the growth of crystalline face-centred cubic Co nanoparticles from small nanoparticles within a Co-rich region in the near surface. The as-implanted and EBA samples are ferromagnetic with Curie temperatures above 300 K. The saturated magnetic moment per implanted Co atom was measured to be as high as 4.25 ± 0.5 μB. The moment per Co atom decreases and approaches that of bulk Co with increased EBA time. This suggests that there may be a ferromagnetic Co1-xSixOyphase that has not been previously reported. An exchange bias is observed and proposed to arise from a thin antiferromagnetic CoO layer surrounding the Co nanoparticles. We find a room temperature magnetoresistance as high as 22.8% at 8 T with linear behaviour above ~ 3 T. The linear magnetoresistance is likely to be due to a geometric magnetoresistance that is observed in inhomogeneous nanomaterials containing metallic nanoparticles in a semiconducting matrix. Thus, EBA leads to Co nanoparticles that are expected to be electronically spin polarized but there is no evidence for spin-dependent tunnelling. These unique characteristics could provide the base for novel devices.

Photostability measurements were made on host–guest thin films containing nonlinear optical chromophores with an indoline donor and amorphous polycarbonate. We find that the indoline-based chromophores are nearly 10 times more photostable than an analogous compound previously studied and which has a dihydopyridine donor. There is an enhancement of the photostability with increasing chromophore concentration and conjugation length. This can be attributed to a reduction in the average separation between the chromophores and excited state singlet energy transfer to adjacent chromophores followed by eventual nonradiative decay. This leads to a reduction in the singlet oxygen generation rate as the chromophore concentration or conjugation length is increased.

An electrically modulated diffraction grating has been demonstrated in poled polymer thin films containing the organic nonlinear optical chromophore, PYR-3 (2-{3-Cyano-4-[3-(1-decyl-1 H-pyridin-4-ylidene)-propenyl]-5,5-dimethy l-5 H-furan-2-ylidene}-malononitrile), and amorphous polycarbonate. A dc electric field induced change in the diffraction efficiency of up to 9% was observed. The diffraction efficiency modulation was likely due to an electric field induced change in the film thickness via a piezoelectric effect rather than via an electronic linear electro-optic effect.

A portable fibre optic dosimeter has been developed that uses transparent fluroperovskite dosimeters at the end of a multimode polymer fibre. It uses two stimulation sources that take advantage of the bimodal trap distribution so that the dose rate and cumulative dose can be monitored. Photoluminescence (PL), optically stimulated luminescence (OSL) and radioluminescence (RL) measurements were made on nearly tissue equivalent NaMgF3:Eu2+, NaMgF3:Mn2+, and high sensitivity RbMgF3:Eu2+ and CsCdF3:Mn2+. Initial dose rate and dose measurements were made using our fibre dosimeter during and after exposure to 60 keV gamma rays.

Bragg gratings were inscribed in poled host-guest polymer thin films containing anelectro-optically active chromophore. Probing the grating in reflection, with a transparent con-ducting electrode on one side of the film and a gold-coated electrode on the other, a modulatingelectric field was observed to induce a modulation in the grating efficiency consistent with thatexpected from the measured electro-optic coefficient.

We report a high electo-optic coefficient (r33) of 175 pm/V in guest-host polymer films made by mixing amorphous polycarbonate with the chromophore, PYR-3 that was synthesized by our team. We have previously shown that PYR-3 has a large 2nd order nonlinear optical figure of merit. The measured r33 is five times larger than that of conventional inorganic materials such as lithium niobate. The decay of r33 with time has been studied for more than 1000 hours at room temperature and ambient atmosphere, and we find that the r33 value gradually reduced to a stable value of 34 pm/V after 40 days.

In this paper we report the results from characterization and optical measurements on samarium doped KMgF3 nanoparticles. Photoluminescence (PL) is observed that can be attributed to Sm2+ and Sm3+. The Sm2+ temperature dependent PL lifetime data can be interpreted in terms of back transfer from the 5D0 level to the lowest 5d level followed by non-radiative decay from the 5d level.

We have fabricated surface magnetic iron nanoclusters using low energy Fe+ implantation and electron beam annealing. We find that changing the fluence has a significant effect on the nanocluster growth, structural and magnetic properties. Low fluences lead to small nanoclusters and superparamagnetism, while high fluences result in larger chain-like nanoclusters that have high remnant magnetizations and a significantly reduced saturation field. Our results show that the nanostructure and the magnetic properties can be tuned by varying the Fe+ fluence, which means that a reliable method can be used to make surface nanoclusters for a variety of applications (e.g. large magnetoresistance sensors with no hysteresis).

We observe a large magneto-resistance in very thin Ba2FeMoO6 films of ~-12% at 10K, which is not significantly changed when thin NiFe/Ba2FeMoO6 bi-layers are made. This suggests that the magneto-resistance in both cases is dominated by inter-grain tunnelling in the Ba2FeMoO6 thin film. There is an anomalous peak in the resistance at ~300K in the bi-layer film that can not be easily explained. However, we know that the temperature where this peak occurs is close to the Ba2FeMoO6 Curie temperature.

We report the results from magnetotransport measurements on polycrystalline Sr2-xLaxFeMoO6 samples at magnetic fields of up to 8 T. We observe a normal as well as an anomalous Hall effect. We find that there is a small decrease in the normal Hall coefficient for La doped samples.

Raman measurements were made on polycrystalline Bi2􀀀xPbxSr1:6Ln0:4CuO6􀀀[removed info] for Ln=fLa,Nd, Sm, Eug with various x and doping states. Our measurements suggest a signi cant Bicontribution to the 118cm􀀀1 mode but not to the 70cm􀀀1 mode which instead shifts to lowerfrequencies with increasing number of CuO2 layers in the Bi-based family. Shifts in the O(2)Srapical oxygen mode can be attributed to unit cell contraction within experimental error.

NMR spin shift data of La1:85Sr0:15CuO4, HgBa2CuO4+[removed info] at ambient pressure, andof YBa2Cu4O8 at pressure up to 63 kbar are discussed that fail the traditional single-electronicuid picture used for the discussion of NMR data. Instead the results point to a commonexplanation for all three systems in terms of two electronic components. One of them hasa temperature-dependent magnetic susceptibility while the second component, as well as itscoupling to the rst component, are constant above the superconducting transition temperatureTc. All susceptibilities vanish below Tc.

Very recently, nuclear magnetic resonance (NMR) of 209Bi has been shown to provide quantitative access to the bulk band inversion in the topological insulator Bi2Se3and detected a highly unusual field induced charge rotation that was found also in the closely related topological insulator Bi2Te3. These observations revealed special properties of the electronic fluid but also reshaped the comprehension of NMR in strongly spin–orbit coupled systems. Here, 209Bi NMR of Bi2Te3of two single crystals with different carrier concentrations is presented, which expands the experimental basis of the unusual charge rotation and the related nuclear spin–lattice relaxation mechanism.