Experimental Solid State Physics Department
List of publications (since 1994)
Our research is aimed to study alloy systems which are far from the equilibrium predicted by the phase diagrams. These systems are interesting for the solid state research as they reveal the properties of phases which were unknown before. These systems are especially important for the practical applications - and this way for the materials science studies - as many non-equilibrium phases have excellent magnetic, mechanical and corrosion properties.
Sample preparation
Different devices are used to prepare non-equilibrium alloys from liquid, solid and vapour phase precursors. In our laboratory we use a special melt quenching unit which enables the handling of small mass (1-2 g) alloy pieces in vacuum or protective atmosphere, facilitating sample preparation even for expensive (e.g. isotopically enriched) materials. Melt quenching of larger quantities is possible in the Metallurgical Laboratory of our Institute.
Surface laser melting is a special case of non-equilibrium melt solidification. For this purpose we use a 0.5 mm diameter focused pulsed NdYAG laser beam (20 ns pulse length and 25 mJ energy) which is moved at the surface by a X-Y table, enabling the treatment of an approximately 10 x 10 mm area.
Non-equilibrium alloys can be prepared by evaporation in ultra vacuum (10-8 mbar) environment using an electron beam evaporation unit controlling two independent sources. The machine utilises a liquid nitrogen cooled substrate holder system and is also equipped with a computer controlled thickness monitor. The system is also capable to produce multilayers and the subsequent thermal treatment is one of the procedures used to produce non-equilibrium alloys in the solid state.
For this later purpose ball milling devices are also used: a Fritsch type planetary mill for the treatment in protective atmosphere and vibratory mills which are continuously pumped by a turbomolecular unit.
Physical Studies
The non-equilibrium phases are studied by calorimetry, magnetic and Mössbauer spectroscopic measurements. The thermal behaviour is investigated in the 100-1000 K temperature range by a Perkin-Elmer type DSC-2 differential scanning calorimeter. A special home developed device enables full computer control of the measurement, including even temperature modulated measurements.
Besides the ac (0-100 kHz) and dc equipment for studying soft magnetic properties, a Foner-type vibrating sample magnetometer is also used to measure the magnetisation in the 15-800 K temperature and in the 0-1.8 T external magnetic field range. The 2*10-4 emu sensitivity of the magnetometer is appropriate for most of the studies except for thin film and multilayer investigations. For this purpose the infrastructural fund of the National Technical Development Board (OMFB) financed in May 1998 the installation of a Quantum Design type SQUID (Superconducting Quantum Interference Device) magnetometer attaining 10-8 to 10-7 emu sensitivity in the 1.8-400 K temperature and in the 0-5 T external magnetic field range. Besides the standards parts, the RSO measuring head unit (Reciprocating Sample Option) was also bought, enabling an order of magnitude higher sensitivity. Three years later (in March 2001) the fund made it possible to upgrade the SQUID magnetometer by purchasing two further options. The ac susceptometer option works in the 0.01-1000 Hz frequency and in the 0-2 Oe ac field amplitude range. The high temperature oven option operates in the 300-800 K temperature range.
Mössbauer spectroscopy is used to study the local environment of Fe atoms in alloys and compounds. We have several transmission spectrometers in our laboratory which can investigate 1-50 micrometer thick samples in the 1.5-1000 K temperature range.
The APD closed cycle cryostat is especially suitable for long time measurements in the 15-300 K temperature range without the use of expensive cryogenic liquids. In the
1.5-300 K temperature range we can also perform measurements in external magnetic field up to 7T, using a Janis cryostat equipped with a superconducting split-coil magnet.
Near surface layers (100-300 nm thickness) can be studied by detecting the conversion electrons in a CEMS spectrometer. The cryosystem, which extends the temperature range of this measurement is under development.
The accumulated almost thirty years' experience in the field of Mössbauer spectroscopy and our self-developed computer programs for evaluating even the most complex spectra make possible to compare the local chemical, topological and magnetic structure of the non-equilibrium alloys with the respective environments well characterised in equilibrium systems by other (e.g. diffraction) methods. In the last years we were awarded some National Scientific Research Fund (OTKA), an Academic Research Fund (AKA) and a Copernicus project besides a number of Instrumental Development Grants.
The yearly scientific funding is near to HUF 5 Million ( approximately 20 kEuro). The research personnel of the group is active in the solid state physics education at the Roland Eötvös and at the Technical University of Budapest. They are also involved in refereeing for the highest ranking journals of the field. They published more than 180 papers which received above 2000 independent citations.
Further information:
Tamás Kemény, E-mail: 
Imre Vincze, E-mail: 
X-ray Laboratory
List of publications (since 1994)
The main line of its research is the study of the atomic structure of solids. Several methods are used depending on the form of the samples and the parameters to be determined. The laboratory is equiped for the study of single crystals, powders and thin layers.
Single crystals (characteristic size ~0.1 mm) are measured by single crystal diffraction technique. This allows the determination of the atomic or molecular structure unknown subtances. There is a possibility to measure at non ambient conditions (25-300 K and max. 50 Kbar).
Powders (individual crystallites tipically have less than 1 mikron diameter) are measured by x-ray powder diffraction. More than 1 mg powder is necessary to take a good quality pattern. There is a possibility to measure as a function of temperature (100-1000 K ). The concentration of known phases can be determined from powder data.
Thin layer samples have large, smooth and flat surface. They can be composed of a single or a multilayer on a substrat. Layer thickness (in the range of 5-100 nm), periodicity (in the range of 5-50 nm) and surface/layer roughness can be determined.
X-ray holographic measurement on NiO. Left upper panel shows the measured Kossel line pattern, together with the hologram, which has a much smaller amplitude. The hologram of the atoms surrounding the Ni atom is depicted on the right upper panel. The 3D real space arrangement of atoms is shown on the lower panel, as reconstructed from the hologram. Click on the image to get a better view (290kB).
Beside these traditional methods the group is working on the development of new techniques for structure determination. In the last few years two methods, the nuclear resonant scattering of gamma rays from powders, and the atomic resolution x-ray holography were developed. The first one can be used to study the relation of hyperfine fields and crytal structures in powdered samples containing Mössbauer isotopes. The x-ray holography gives information on the local atomic environment of selected elements in three dimensions. The application of the above methods are not wide spread yet. Further theoretical and experimental work is necessary to implement them in commertial equipments.
Most important fields of research: Structural study of fullerenes, nuclear scattering, x-ray holography.
Further information:
Gyula Faigel, E-mail: 
Theory of phase transitions
Please see this detailed description.
Further information:
László Gránásy, E-mail: 
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Last modification: 2009-02-09 13:35:12
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Departments > Experimental Solid State Physics
