STATE OF THE ART
(A) Materials for Spintronics Applications
In the last decade, there has been a growing interest for the study of nanopatterned structures combining magnetic materials with nonmagnetic metals and/or semiconductors motivated by possible spintronic applications . In spintronics, the information carrier is not the electron charge but the electron spin, and this offers fascinating opportunities for a new generation of devices combining standard microelectronics with spin-dependent effects. A highly promising category of materials for such applications are transition metal oxides, which in certain cases exhibit full spin polarization. However, in all efforts to understand these materials and use them for fabricating prototype new devices, there are considerable difficulties and challenges: Electronic properties of 3d transition metal oxides (i. e. Ti, Mn, Fe, Cr, Co, Cu oxides) are much more complex and less understood than those of elemental metals, or oxide ionic insulators. Hence, there is a continuing need for fundamental studies before the potential of these materials for spintronic applications can be fully realized. In this framework the project will be focused in understanding the fundamental physics, which controls the magnetotransport properties of La based manganites, such as La1-xDixMnO3 with Di=Ca, Sr, Ba and spinel Ferrites, in bulk and thin films.
(B) Materials for Nanocomposite Magnets:
Magnets are an essential part of our daily life. A key factor determining their performance is the maximum energy product (BH)max. Rare-Earth permanent magnets based on a single magnetic phase have nearly reached their theoretical limit. However, it is possible to increase the maximun values (BH)max with the use of nanocomposite magnets. Such nanocomposites consist of two or more different magnetic phases, where the inter-granular exchange interaction leads to a co-operative magnetization behavior (these are sometimes referred to as “exchange-spring magnets”), offering the possibility to combine the advantages of a high-anisotropy hard and a high-magnetization soft phase. The challenges which must be addressed for a successful development of nanocomposite magnets include (i) the fabrication of pure phase, soft and hard nanoparticles, (ii) the mixing of nanoparticles without agglomeration, (iii) the alignment despite their extremely small volume and (iv) the consolidation without grain growth, excessive inter-diffusion or decomposition (for the Sm2Fe17Nx nanoparticles).
(C) Modified Nanomagnets in Colloids for Biomedical Applications:
Iron based nanostructured materials in colloids have found widespread Biomedical applications ranging from Contrast Agents for Magnetic Resonance Imaging (MRI) up to Magnetic Hyperthermia and Targeted Drug Delivery agents for Cancer treatment. Magnetic nanoparticles have found their way into some clinical applications; however significant improvements in performance (R2 relaxivity, hyperthermia and magnetic force) should be accomplished. For example in magnetic resonance imaging, inherent problems such as broad particle distribution, low value of the saturation magnetization of the nanoparticles as compared to the bulk samples, particle aggregation in a magnetic field, and particle sedimentation in physiological media remain unsolved or difficult to address The challenges which must be addressed for a successful development of nanocrystalline iron based particles including magnetic iron oxides and metallic iron nanoparticles are: (i) the synthesis of highly crystalline nanoparticles with controlling size in the range of 5-20 nm and monodispersity (SD<10%) (ii) the appropriate surface functionalization in order to make the nanoparticles highly water soluble and additionally functional for specific interactions (e.g. positively or negatively charged) (iii) the development of chemical processes for controllable nano-aggregate formation.