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NiOx nanoconstrictions 20–40 nm wide on SiO2/Si substrates exhibit nonlinear and asymmetric I-V characteristics, which are greatly affected by applied magnetic or electric fields. This behavior is attributed to the generation of magnetic conducting paths in magnetically frustrated nonstoichiometric NiOx material. The room-temperature resistance can be changed by factors of several hundreds. This property, if well controlled, is potentially very attractive for spintronic devices. [ABSTRACT FROM AUTHOR]

Point contacts of magnetite exhibit large, reversible increases of conductance by a factor of up to 5 in the presence of a small magnetic field (<10 mT), provided the conductance is less than the quantum of conductance G0 (12 900 Ω)-1. Smaller effects are found in (La0.7Sr0.3)MnO3 and Co2Cr0.6Fe0.4Al. Comparable effects observed in magnetite nanoconstrictions milled using a focused-ion beam in thin films deposited on oxide substrates are only reversible on a time scale of hours. High-resistance nanogaps show evidence of field emission beyond a voltage threshold, which is itself field dependent. The results are discussed in terms of spin-polarized transport, magnetostriction, magnetic dipole strain, and Fowler–Nordheim tunneling. [ABSTRACT FROM AUTHOR]

Nickel nanoconstrictions about 20 nm wide produced by electron beam lithography in a 60 nm nickel film exhibit resistivities in the kΩ range with a nonlinear and asymmetric I - V characteristic. Noise spectra of the contacts sometimes deviate from 1/f behavior due to random telegraph fluctuations at room temperature with a frequency in the 10 Hz range. The resistance fluctuations between the two states are about 0.1%. The time spent in the high resistance state increases as we increase the temperature, and the discrete fluctuations eventually disappear with an increase of the temperature of more than about 15 °C. An explanation is proposed in terms of electron-wind electromigration which interacts with the narrow domain wall formed at the nanocontact. [ABSTRACT FROM AUTHOR]

A method is described for the fabrication of magnetic force microscopy tips via localized electrodeposition and focused ion beam milling departing from commercial tapping mode tips. Very high aspect ratios and interacting magnetic moments are possible without altering significantly the tapping resonant frequency of the cantilever. These tips can achieve high magnetic resolution at room temperature and open atmosphere. They can also be fabricated into any shape, with applications for ferromagnetic resonance measurements and nano-imprinting. [ABSTRACT FROM AUTHOR]

We have studied the transport properties of mechanically stable Fe3O4 and La0.7Sr0.3MnO3 nanoconstrictions patterned by focused ion-beam milling. The magnetoresistance decreases with the square of the applied voltage and scales with the resistance of the constriction, with values up to 8000% for magnetite and 100% for La0.7Sr0.3MnO3. These results are interpreted within a model for domain-wall magnetoresistance. Some samples exhibit electrical hysteresis with discrete changes of resistance that disappear in the presence of a magnetic field, indicating domain-wall displacement driven by a spin-polarized current. [ABSTRACT FROM AUTHOR]

We present a joint experimental and theoretical study on the transport properties of nickel nanoconstrictions. The samples show highly non-linear and asymmetric I–V characteristics when the conductance is smaller than G0=2e2/h, and huge magnetoresistance ratios exceeding 99.9%. We model a single point contact in a two-band tight-binding model as a 2×2 nickel chain connected to two semi-infinite nickel leads. The magnetoresistance is calculated by using a non-equilibrium Green''s function technique. [Copyright &y& Elsevier]

We generate a new air-stable pseudo-D 5h Dy(iii) Single-Molecule Magnet (U eff = 1108 K, T B = 14 K) by combining a weak equatorial ligand field from a macrocyclic L N5 ligand with a strong axial ligand field. Based on our synthetic blueprint, we use ab initio calculations to show the vast scope for macrocyclic engineering of magnetic anisotropy.

A new air-stable sulfur-ligated Dy(iii) single-ion magnet has been successfully isolated with Ueff = 638 K and hysteresis loops open up to 7 K. In silico studies show that the S co-ligands significantly boost the axiality and that Te- and Se-donors have the potential to further enhance the magnetic properties.

A new nine-coordinate, air-stable Dy(iii) single-ion magnet has been successfully isolated. Our in silico studies demonstrate that through carefully modulating the ligand electronics, the axiality can be boosted to generate Ucal barriers of over 600 K.

Chemical composition, size and structure of the nanoparticle are required to describe nanoceria. Nanoparticles of similar size and Ce(III) content might exhibit different chemical behaviour due to their differences in structure. A simple and direct procedure based on affordable techniques for all the laboratories is presented in this paper. The combination of Raman and UV-vis spectroscopy and particle impact coulometry (PIC) allows the characterization of nanoceria of small size from 4 to 65 nm at a concentration from micromolar to nanomolar, a concentration range suitable for the analysis of lab-prepared or commercial nanoparticle suspensions, but too high for most analytical purposes aimed at nanoparticle monitoring. While the PIC limits of size detection are too high to observe small nanoparticles unless catalytic amplification is used, the method provides a simple means to study aggregation of nanoparticles in the media they are needed to be dispersed for each application. Raman spectroscopy provided information about structure of the nanoparticle, and UV-vis about their chemical behaviour against some common reducing and oxidizing agents. Graphical Abstract To characterize nanoceria it is necessary to provide information about the shape, size and structure of the nanoparticles as well as the chemical composition.

The protein ferritin has a natural ferrihydrite nanoparticle that is superparamagnetic at room temperature. For native horse spleen ferritin, we measure the low field magnetic susceptibility of the nanoparticle as 2.2 x 10(-6) m(3) kg(-1) and its Néel relaxation time at about 10(-10) s. Superparamagnetic nanoparticles increase their internal energy when exposed to radio frequency magnetic fields due to the lag between magnetization and applied field. The energy is dissipated to the surrounding peptidic cage, altering the molecular dynamics and functioning of the protein. This leads to an increased population of low energy vibrational states under a magnetic field of 30 microT at 1 MHz, as measured via Raman spectroscopy. After 2 h of exposure, the proteins have a reduced iron intake rate of about 20%. Our results open a new path for the study of non-thermal bioeffects of radio frequency magnetic fields at the molecular scale.

Ferritin, the iron cage protein, contains a superparamagnetic ferrihydrite nanoparticle formed from the oxidation and absorption of Fe(2+) ions. This nanoparticle increases its internal energy when exposed to alternating magnetic fields due to magnetization lag. The energy is then dissipated to the surrounding proteic cage, affecting its functioning. In this article we show that the rates of iron chelation with ferrozine, an optical marker, are reduced by up to a factor of 3 in proteins previously exposed to radio frequency magnetic fields of 1 MHz and 30 microT for several hours. The effect is non-thermal and depends on the frequency-amplitude product of the magnetic field., ((c) 2009 Wiley-Liss, Inc.)

A study of urticarial syndrome is carried out at the "Ciro Redondo García" Municipality General Hospital, Artemisa. The clinical history of children hospitalized during 1988 in the Miscellaneous Ward were reviewed. Nurse care is valued. It was found that 9.4% of hospitalization corresponded to such disease and that urticaria was the most frequent form of presentation and in the group aged 5-14 years. Mean hospital stay was 5 years. Food was the prevailing cause of this disease and there was not chronic clinical forms.