Bulk oxide and chalcogenide materials

Bulk oxide and chalcogenide materials
Dr. A. C. Komarek
Dr. D. Michailova
Dr. J. Yang
Dr. Z. Li
Dipl. Phys. Y. Drees
Subakti
M. Sc. C. Koz
Dr. A. Sarapulova
B. Sc. P. Reichel
A. Keil
Instrumentation & Methods

materials development     neutrons & X-rays     physical properties

CSI (CSC) floating zone 4-mirror furnace

For the study of physical properties of condensed matter the synthesis of high quality single crystals is crucial, especially for polarization dependent soft-X-ray absorption (XAS), soft/hard-X-ray photoelectron spectroscopy (PES) and neutron scattering experiments.
The CSI (CSC) floating zone image furnace works with 4 ellipsoidal mirrors. Different growth atmospheres with pressures of the order of 10 bar (~pressure 100 m deep in the ocean) are applicable.

Floating zone image furnace with 4 ellipsoidal mirrors Floating zone image furnace with 4 ellipsoidal mirrors
ellipsoidal mirrors Floating zone growth

responsible: ..Dr. A. C. Komarek . komarek[at]cpfs.mpg.de ..

>>> Time schedule <<<

HKZ floating zone (high pressure) mirror furnace

Working with one ellipsoidal mirror around the sample chamber the HKZ floating zone image furnace is able to apply extremely high pressures of up to 150 bar (~pressure 1.5 km deep in the ocean) .

HKZ high pressure quartz glass 1 ellipsoidal mirror view into sample chamber growth process

responsible: ..Dr. A. C. Komarek . komarek[at]cpfs.mpg.de ..

>>> Time schedule <<<

Horizontal furnaces

Horizontal furnaces for solid state reactions with different growth atmospheres available.

tubular furnaces

responsible: ..Dr. A. C. Komarek . komarek[at]cpfs.mpg.de ..

Real-time X-ray Laue system

Also a real-time Laue camera for checking the single-crystallinity of an as-grown crystal as well as for quick (→ one or few seconds per image) and comfortable (→ remote control of goniometer) crystal-orientation using W X-ray radiation is available.

Laue X-ray diffraction pattern of floating zone grown Ca2RuO4 single crystal
RT-Laue image of
Ca2RuO4 (ACK388)

responsible: ..Dr. A. C. Komarek . komarek[at]cpfs.mpg.de ..

Powder and Single-crystal X-ray diffraction

In a scattering process the three-dimensional periodic electron density in the crystal splits the X-ray beam in several components Fhkl, i. e. the scattering process is equivalent to a Fourier transformation of the electron density in the crystal and the measured intensities are proportional to the square of the amplitude of the complex structure factors Fhkl. By measuring these intensities in powder and single crystal X-ray diffraction measurements, information going deep into the details of the crystal structure can be obtained.

X-ray scattering for different wavelengths X-ray diffraction pattern of floating zone grown Ca2RuO4 single crystal
X-ray pattern of
Ca2RuO4 (ACK392)
blue/yellow/red sine waves: hard X-rays / X-rays / soft X-rays
red/white/blue spheres: atoms
grey lines: unit cell


♦ X-rays emitted from sealed X-ray tube or in synchrotron rings from electrons or positrons accelerated to relativistic energies (several GeV, i.e. 99.9999...% of the speed of light )
♦ 2 d sin θ = ν λ (scattering condition / Bragg law)

responsible: ..Dr. A. C. Komarek . komarek[at]cpfs.mpg.de ..





Neutron scattering

Neutron experiments can be performed in reactor neutron sources (fission of Uranium) or in spallation neutron sources. In contrast to X-rays, neutron diffraction results from the nuclear interaction between neutrons and cores (and not from interaction with the electron shells) as well as the magnetic interaction of the neutrons magnetic moment with the moments of the atoms. The most important consequences arising from the properties of neutrons are listed in the following:
- large penetration depth
- large scattering contributions from light elements as hydrogen and oxygen
- different scattering from elements with similar atomic numbers allows to distinguish between these elements
- different scattering from isotopes allows to study for example specific parts of molecules which have been deuterated etc.
- measurement of excitations accessible since the neutron energy is comparable to the energy of elementary excitations in matter
- measurement of magnetic structure and dynamical magnetic properties is possible due to the magnetic moment of the neutron.

neutron scattering with 2D incommensurate electron spin arrangement
white spheres: neutrons
red spheres: protons
arrows: electron spins

235U + n → 236U → 144Ba + 89Kr + 3 n (chain reaction; in average: 1.5 n emitted)
♦ d2σ/dΩdω = (γr0)2(kf/ki) F(Q)2 exp(-2W(Q)) ∑α,βα,β-QαQβ/Q2) Sαβ(Q,ω)
→ n couples to electron spin (moment) perpendicular to the scattering vector Q

responsible: ..Dr. A. C. Komarek . komarek[at]cpfs.mpg.de ..





PPMS

Physical properties measurement system (PPMS) can be used for measuring resistivity, ac-transport, Hall-effect and heat capacity of solids in the temperature range 1.8 K - 400 K and in magnetic fields up to 9 T.

PPMS

responsible: ..Dr. S. Rößler . sahana.roessler[at]cpfs.mpg.de ..





SQUID Magnetometer

A SQUID magnetometer can be used for measuring the magnetic susceptibility in a wide temperature and field range.

SQUID Magnetization (H || c-axis) of  floating zone grown Ca2RuO4 single crystal
c-axis magnetization of
Ca2RuO4 (ACK388)

responsible: ..Dr. S. Rößler . sahana.roessler[at]cpfs.mpg.de ..





Single crystal X-ray diffractometer

A single crystal X-ray diffractometer with bent (focusing) monochromator for highest intensity performance (more than factor x3 intensity enhancement) equiped with the novel Photon 100 large area detector based on latest CMOS technology gives rise to precise structural investigations, electron density measurements or the detection of weak superstructure reflections.

Single crystal X-ray diffractometer measured intensities in reciprocal HK0 plane of floating zone grown Ca2RuO4 single crystal
detected reflections in HK0 plane of untwined
Ca2RuO4 (ACK388)

responsible: ..Dr. A. C. Komarek . komarek[at]cpfs.mpg.de ..



impressum


Real time Laue camera Real time Laue camera Real time Laue camera