We experimentally show that it is possible to induce room-temperature ferromagnetic-like behavior in ZnO nanoparticles without doping with magnetic impurities but simply inducing an alteration of their electronic configuration. Capping ZnO nanoparticles ( approximately 10 nm size) with different organic molecules produces an alteration of their electronic configuration that depends on the particular molecule, as evidenced by photoluminescence and X-ray absorption spectroscopies and altering their magnetic properties that varies from diamagnetic to ferromagnetic-like behavior.

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Magnetic Properties of ZnO Nanoparticles

Role of defects in tailoring structural, electrical and optical properties of ZnO

Porosity and photocatalytic studies of transition metal doped ZnO nanoclusters

Increase of Co solubility with decreasing grain size in ZnO

The production and the supply of high quality laboratory animals have fundamental importance for the accomplishment of vanguard scientific research, with reproducibility and universality. The quality of those animals depends, largely, of the available facilities for their production and lodging, to assure the demanded sanitary control and animals’ welfare, in agreement with the ethical principles that control the activity. The facilities also have to fill out other requirements, such as: the functionality of the environments to make possible the suitable and efficient handling of the animals, facilitating the execution of the routine activities; the respect to ergonomic principles to provide a safe environment and the operators’ well being. The facilities design is of vital importance so that the mentioned requirements can be reached. The project of the Nuclear and Energy Research Institute (IPEN) Animal House Facilities was accomplished in the year of 1964. However, by that time there were not the current recommendations with respect to the sanitary, genetic and environmental controls. The facility was planned with the objective of being a production unit and a local for keeping of defined animals from sanitary, genetic and environmental point of view. Nevertheless, the original unit drawing presents an unsuitable distribution of the area where animals are stocked and also different activities are performed. The Animal House Facilities occupy an area of 840 m, with one pavement, where the production areas and the stock of original animal models of the own Institution are distributed, as well as the maintenance of animals from other national or foreigner institutions. It supplies rats and mice for biological tests of radiopharmaceutical lots, produced in IPEN, before they be sent to hospitals and clinics spread out in Brazil, for use in Nuclear Medicine. It also supplies rats and mice for tests of odontological materials, for tests with growth hormones and for researches of new pharmaceuticals and radiopharmaceuticals, among others applications. Many of the animals models produced in IPEN are unique in Brazil and they constitute, therefore, an important patrimony that should be preserved. This paper describes the activities that have been executed in Animal House Facilities of IPEN, including the refurbishment project and the adaptation of the facilities.

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Instituto de Pesquisas Energéticas e Nucleares

We report here on the magnetic properties of ZnO:Mn- and ZnO:Co-doped nanoparticles. We have found that the ferromagnetism of ZnO:Mn can be switched on and off by consecutive low-temperature annealings in ${\mathrm{O}}_{2}$ and ${\mathrm{N}}_{2}$, respectively, while the opposite phenomenology was observed for ZnO:Co. These results suggest that different defects (presumably $n$-type for ZnO:Co and $p$-type for ZnO:Mn) are required to induce a ferromagnetic coupling in each case. We will argue that ferromagnetism is likely to be restricted to a very thin, nanometric layer at the grain surface. These findings reveal and give insight into the dramatic relevance of surface effects to the occurrence of ferromagnetism in ZnO-doped oxides.

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Reversible ferromagnetic switching in ZnO:(Co, Mn) powders

Structural and magnetic properties of ZnO:TM (TM: Co, Mn) nanopowders

Magnetoresistive ceramics, based on half-metallic ferromagnetic oxides have received renewed attention in the last few years because of their possible applications. Here, we review some recent progress on the development of magnetoresistive ceramic materials such as La 2 / 3 Sr 1 / 3 MnO 3 and Sr 2 FeMoO 6 ceramic materials. We shall revisit their basic properties, the strategies that have been employed to understand and to improve their intrinsic properties, pushing the limits of their operation at temperatures well above room-temperature, and the development of some applications. This effort has required the contribution of a number of actors. Starting from research laboratories, it has progressively involved industries that nowadays are able to supply high quality raw-materials or to manufacture magnetoresistive components at large scale.

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Magnetoresistive ceramics. Recent progress: from basic understanding to applications

Half-metallic ferromagnetic oxides present a remarkable potential for the development of magnetoresistive sensors. We report on the design, construction and test of a contact-less on–off position sensor based on thick La2/3Sr1/3MnO3 films. Films were fabricated on polycrystalline Al2O3 substrates by means of the standard screen-printing technique. The temperature dependence of the output signal of the sensor has been monitored from room temperature up to 120 °C.

On–off magnetoresistive sensor based on screen-printed La2/3Sr1/3MnO3 manganite

We report here on the magnetic properties of ZnO:Mn and ZnO:Co doped nanoparticles. We have found that the ferromagnetism of ZnO:Mn can be switched on and off by consecutive low-temperature annealings in O2 and N2 respectively, while the opposite phenomenology was observed for ZnO:Co. These results suggest that different defects (presumably n-type for ZnO:Co and p-type for ZnO:Mn) are required to induce a ferromagnetic coupling in each case. We will argue that ferromagnetism is likely to be restricted to a very thin, nanometric layer, at the grain surface. These findings reveal and give insight into the dramatic relevance of surface effects for the occurrence of ferromagnetism in ZnO doped oxides.

Ll. Aragones

Papers

Reversible ferromagnetic switching in ZnO:(Co, Mn) powders

Structural and magnetic properties of ZnO:TM (TM: Co, Mn) nanopowders

Magnetoresistive ceramics. Recent progress: from basic understanding to applications

On–off magnetoresistive sensor based on screen-printed La2/3Sr1/3MnO3 manganite

Reversible Ferromagnetic Switching in Zno:(Co,Mn) Powders