Development of advanced ultrasensitive characterization tools for nanostructured materials investigations

Research on nanomaterials and development of related devices require state-of-the-art fabrication and characterization tools. For this reason the equipments in Fabrika need to be updated for the preparation of materials by growth methods equipped with ultrasensitive in-situ and ex-situ characterization techniques.

6a) Many-purpose facility on the basis of the proton and ion Linac at IKBFU

(Team leader: Alexander Goikhman)

The project aims to create the first Kaliningrad facility based on a proton and ion accelerator, which would make it possible to conduct interdisciplinary research. Charged particle injection devices and target modules make it possible to use the facility for solving problems in the field of materials science, radiation physics of solids, biology, medicine, and processing and modification of materials properties, education of students of the Baltic federal university.  It is planned to work with both charged particle beams and secondary radiation, in particular, neutrons. The particle beam-based methodologies for diagnosing and modifying materials are complementary to numerous methodologies used at the Fabrika science park of the Immanuel Kant Baltic Federal University (IKBFU), whose research and technological potential will increase after the accelerator is launched. In a long-term perspective, this facility can become the core of the University’s centre for particle and radiation treatment for cancer. This will be conducted in the framework of developing research at the interface of medicine and physics. The accelerator and auxiliary equipment will contribute significantly to the regional educational platform. Graduate and undergraduate students and employees of IKBFU and other regional universities will have an opportunity to familiarise themselves with accelerating equipment, beam physics, beam-substance interaction, nuclear reactions, and radiation dosimetry. In the absence of research reactors in the region, an accelerator-based facility will contribute to solving numerous research, technological, and medical problems without a need to use fissile substances and take into account the environmental concerns, safety factors, non-proliferation regime, and creation of restricted access systems. Practical exercises in dosimetry of high energy charged particles irradiation are very important for training of future specialists for the construction and exploitation of the Baltic atomic power station.

6b) Research and development of the microelectronic experimental prototype Device for the Optogenetic Remote Control Functions of the Brain (DORCFB) 

(Team leader: Alexander Goikhman)

Main goal: Development of the semiconductor device implanted into the brain and capable to simultaneously handle and log the activity of brain cells by optogenetic methods.

Main tasks: 

1. To develop a temperature microsensor device for the DORCFB. Development of temperature microsensor will allow for temperature control in order to avoid overheating and damage to the brain cells.

2. To develop an inorganic LED of ptogenetic devices for the DORCFB. Development of this LED allow to provide an optogenetic control activity of brain cells.

3. To establish the optimal device form factor for the DORCFB. Selection and justification of the optimal form factor devices based on the literal and experimental data will reduce the brain damage during insertion of the device and reduce the period of recovery of the brain after insertion of the device.

4. To develop a micro-electrode device for the DORCFB. Development of the micro-electrode will not only carry out the stimulation and / or recording of electrophysiological activity of the brain cells, but to miniaturize the device. 

5. To develop an inorganic micro- CCD for the DORCFB. Development of the  micro CCD will provide inorganic fluorescent registration signals received from the activated and / or stimulated cells in the brain.

Selection and study of all the optimal characteristics of the developed components and the device for optogenetic control brain functions will be carried out both on the basis of literature data and the experimental data by determining the specifications and then testing each part separately and the whole unit in vitro cell culture, ex vivo on experiencing brain slices and in vivo brain of a living animal. The use of biocompatible materials as well as the bases of the substrate and device size reduction will reduce the trauma and prevent inflammation in the brain. Thus, the development of ultra-thin, flexible, multi-function opto-electronic system will be provided, mounted on the implant needle, for delivery to the deep structures of the brain. Fastening system for implant needle using polymer biodegradiruemoego allow removing the needle from the brain after the administration system in the brain.

The result of these tasks is to create ultra-thin technology, biocompatible, with minimal trauma to the introduction of invasive optoelectronic assembly in the soft tissues of the brain of mammals, which opens a wide potential for further use in translational biomedicine.

Collaborating Institutes offering characterization techniques and expertise which are not available at IKBFU

University of Duisburg-Essen (Michael Farle)

a) Spin dynamics and spin logic in magnetic nanostructures for spintronic devices

(Michael Farle)

Future energy saving devices in information technology used in computation, logic elements , sensors and information processing and storage will rely on innovations based on magnetic elements which require the manipulation of a quantum mechanical property “the spin”. The dynamics of the spin movement and relaxation in materials of different complex configurations will be studied by microwave resonance experiments in the time and frequency domain with a spatial resolution approaching a few nanometers and picoseconds in the time domain. New conceptual devices, with improved efficiency and reduced amount of dissipated energy will be designed, fabricated and tested. New magnetic materials in which the Dzyaloshinsky Moriya interaction is a dominating interaction will be investigated. In such a materials a new phase, so called Skyrmions, can be stabilized. Very little is known about their dynamics in confined geometries. The confinement effects need to be investigated, since future applications will be based on structures where the geometrical structure of an element approaches the characteristic length scales of the dominating interactions of such materials.

b) Magnetic MAX Phases

(Michael Farle)

In general MAX phases (Mn+1AXn, where n = 1, 2, or 3) are composed of an early transition metal M (Sc, Ti, V, Cr, Mn, Zr, Nb, Mo, Hf, or Ta), an A-group element A (for example Al, Ga, or Ge) and either C or N, denoted X. They are nanolaminated ternary compounds which show unique and intriguing properties ranging from spectacular mechanical to self-healing and superconducting properties. They show properties which are normally associated with either metals or ceramics. Similar to a metal they are electrically and thermally conductive, have high values for strength and modulus, and are damage tolerant. From the point of view of ceramic properties they are elastically rigid, and lightweight, and most of them are resistive against oxidation even at high temperatures. The crystal structure of MAX phases is hexagonal with a repeated M-A-M-X-M-A-M-X atomic layer stacking in the c direction. In 2013, the first magnetic MAX phases where discovered in which the 3d element has been Mn or Cr or a mixture of them. Only very limited work has been performed to measure and understand the magnetic properties (magnetocrystalline anisotropy, magnitude of magnetic moments, contribution of orbital magnetism to the total magnetic moment and magnetic relaxation) which shall be investigated in this project for a selected class of magnetic MAX phases.

Institute of Structure of Matter (ISM), National Research Council, Rome (Dino Fiorani)

a) New high-performance rare-earth(RE)-free (or with reduced content) permanent magnets.

(Gaspare Varvaro)

The risk of supply and the high cost rare-earth (e.g. Nd, Sm, Pr) based and Pt and Pd based (FePt, CoPt L10 phase) based magnets have stimulated computational and experimental investigations on novel and commercially attractive hard magnetic materials based on non-critical, easily accessible, stable and easily recyclable 3d metals like Fe, Co and Ni, with a high saturation magnetization (> 1.2 T) and magnetic anisotropy (K > 1 MJ/m3), suitable for ensuring a maximum energy product approaching or even surpassing that of RE-based PMs.

Recent promising routes consist in inducing a large magneto-crystalline anisotropy in soft FeCo(FeNi) cubic alloys by a template induced tetragonal straining and/or element substitutions, or realizing the L10-fct FeNi alloy, which forms only at the extreme thermodynamic conditions of extra-terrestrial meteorites . L10-FeNi alloy, also known as tetrataenite, is a possible candidate for future RE-free and low-cost permanent magnets due to its large saturation magnetization (1.6 T), high uniaxial magnetic anisotropy (~ 106 J/m3) and a fairly high Curie temperature (up to 550 °C). However, the fabrication of the L10-FeNi phase is extremely challenging due to the low atomic mobility below the chemical order/disorder transition temperature (320 °C) that kinetically limits the formation of the L10 phase. Such phase is naturally founds in meteorites, where it forms over millions of years in extreme temperature/pressure conditions. Different strategies have been proposed to favour the formation of the tetrataenite phase, including deposition of alternate Fe and Ni monoatomic layers, irradiation with neutrons or high energy electrons, or addition of a third element. Only the latter approach is practically exploitable for applications as permanent magnets. The most recent results on ternary FeNiX compounds, where X is a 3d (Ti, V, Cr, Mn, Fe, Co) or a p (Al, P, S) have proved that such additives may facilitate the formation of the tetragonal phase, while their effect on magnetic properties is mostly negative or neutral and promising results were only obtained by the addition of substitutional Fe or Co or interstitial C, B to the structure.   Tetragonal distorted FeCo alloys have recently received a great deal of attention due to their very high uniaxial anisotropy (up to 107 J/m3), which would lead, in combination to their highest saturation magnetization (2.43 T) to an energy product two times larger that current state-of-art Nd-Fe-B magnets. Up to now, the tetragonal distorted FeCo (FeNi) phase was obtained in the form of very thin films or as a particle shell by exploiting the epitaxial strain induced by suitable templates such as Pt (001), Pd (001), Rh (001), Ir (001), AuCu3 (001) substrates or by AuCu nanoparticles, respectively. More recently it was theoretically proved that interstitial B and C impurities may be an effective and commercially attractive way to stabilize the tetragonal distortion in a rather wide range of Fe and Co compositions. Moreover, it has been proved, both theoretically and experimentally, that the addition of small amount of substitutional heavy TM atoms, such as Mo, W, Re, Ir in small atomic percentage to FexCo1-x-based compounds, may lead to an enhancement of magnetic anisotropy for some compositions.

Objectives

- Synthesis of FeCo- and FeNi-based magnetic nanoparticles with high saturation and magneto-crystalline anisotropy. For this purpose two bottom-up synthesis strategies are proposed:

- Template synthesis of core (L10-AuCu)/shell(FeCo, FeNi) nanoparticles in which the L10 phase transformation of the core enables the tetragonal distortion of the epitaxially grown FeCo (FeNi) shell. This strategy was already demonstrated to efficiently trigger a tetragonal reconstruction of FeCo (FeNi) shell within a critical thickness of few nanometers, above which the shell structure relaxes. To overcome this issue, doping of FeCo(FeNi) shell by interstitial light atomic impurities (e.g. C,B,N) will be explored to stabilize the shell tetragonal distortion at larger thicknesses (as successfully obtained in thin film systems) to increase the amount of the magnetic volume and the performance of the final sintered magnet.

- Synthesis of highly ordered tetragonal structures using chemically ordered molecular crystals with Fe and Ni distributed in alternate layers. The feasibility has been demonstrated by the ISM team in the environmentally friendly synthesis of L10 fct FePt nanoparticles, with a high order parameter and degree of fct phase conversion at a much lower temperature than bulk. The extension of the same strategy to the L10 FeNi alloy is expected to allow the synthesis of pure fct metallic nanoparticles by thermally decomposing the precursor molecular crystals in a single highly controlled step, overcoming the biggest difficulty faced in the synthesis of the L10 phase (i.e. the extremely low atomic diffusion of Fe and Ni).

- Study of the angle dependent static magnetic properties as a function of field and temperature.

b) Thin films spinel ferrites for spintronic applications

(Gaspare Varvaro)

3d transition-metal spinel ferrites MFe2O4 (M = Fe2+, Co2+, Ni2+, Mg2+, Mn2+, etc.) are potential candidates for novel (all-oxide) spintronic devices for sensing, information storage and thermoelectric applications, among others. Varying M and the cationic distribution (inversion degree) allows tuning both the magnetic properties (e.g. magnetic anisotropy, the Curie temperature and the saturation magnetization) and the electronic behavior (insulating and half-metal state) according to some specific functions. Half-metal spinel ferrites could serve as the magnetic electrode in tunneling magneto-resistive (TMR) junctions (e.g. spinel ferrite SF/non-magnetic barrier NM/spinel ferrite or ferromagnetic metal FMM) while the insulting counterparts are good candidates for spin-filter (NM metal/SF/NM barrier/FMM) and pure spin current (SF/NMM) devices. In addition to magnetic spinel ferrites, non magnetic spinels have attracted much attention as new materials for the tunneling barrier in TMR junctions. Moreover, due to their high compatibility with other oxides (with different properties) and organic materials, the establishment of high-quality all-oxide multifunctional materials is highly expected. Furthermore, with respect to their metallic counterpart they are environmental stable and many have magnetic critical temperatures well above room temperature.

To fully exploit the merits of spinel ferrites in practical (all-oxide) spintronic devices, the following aspects will be addressed:

-      Developing growth methods and procedures for high-quality film (in terms of both structure and microstructure) to achieve stable half-metallic characteristics and a spin-filter effect at room temperature.

-      Obtaining high quality interfaces between spinel ferrites and barrier in spintronic devices to preserve high effective spin polarization at the interface; in this regard, finding novel non-magnetic spinel barriers is also considered an important issue.

-      Fine tuning of magnetic and electronic properties by modulation of the cation distribution.

-      Integration on silicon looking for CMOS compatibility.

c) Functionalized magnetic nanoarchitectures for magnetic hyperthermia

(Davide Peddis)

Magnetic heating is based on the thermal energy generation via magnetic nanoparticle (MNP) mediators activated by alternating magnetic (AC) field. The gauge of MNP’s heat transfer efficacy is given by specific absorption rate (SAR), also referred to as specific loss power (SLP). In the last years magnetic heating has been widely investigated for several applications in biomedicine (e.g., magnetic hyperthermia) and catalysis.

The heating efficiency of MNPs is affected by several parameters: i) amplitude and frequency of the applied AC field; and ii) the parameters inherent to the nanoparticles such as size, size distribution and shape which in turn govern magnetic properties of the system. Besides conventional approaches for the enhancement of heating efficiency, such as altering the size and/or composition of the MNPs, recently tailoring the MNP’s anisotropy has been investigated as alternative route to increase the magnetic heating power. In particular, the interface exchange coupling (IEC) across a ferro (ferri)magnetic[(F/FI)]/antiferromagnetic (AF) interface can gives rise to an additional anisotropy contribution (exchange anisotropy) allowing to increase the SAR/SLP values

Methodology

In this context, the present project aims at studying the influence of IEC on the magnetic heating efficiency in FI/AF and AF /FI core shell nanoparticles system. First, FI and AF nanoparticles will be prepared separately by using different wet chemical procedures. As a second step a suitable synthetic procedure will be set to prepare FI/AF and reverse AF /FI core shell nanoparticles nanoparticle, changing core size and shell thickness.

Within this frame, the specific objectives of the project are:

i) Defining new protocols for the synthesis of FI/AF core-shell nanostructures

ii) Understanding the effects of interfacing FI /AF materials on magnetic anisotropy of the whole system

iii) Understanding the effects of interfacing FI /AF materials on magnetic heating efficiency