Major Equipment
17 Tesla measurement station
The most powerful superconducting magnet in our lab is capable of generating magnetic fields of up to 17 T. It is contained in a gas flow cryostat, which facilitates control of the sample temperature in the gas cooled mode within a wide range (approximately 5 K – 200 K). Alternatively, flooding with liquid helium is possible, thus enabling measurements at 4.2 K, or down to approximately 2 K using pressure reduction. This system is primarily used to perform transport current measurements on superconducting samples, which can be performed with currents of up to 1000 A.
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Cryostat with wooden covering, control electronics in the background
6 Tesla measurement station
The 6 T measurement station is equipped with a split-coil magnet in a helium flow cryostat which allows measurements at temperatures down to approximately 5 K. Measurements of the anisotropy of the critical current density are possible for samples capable of sustaining high transport currents (up to 150 A), such as coated conductors, as well as for thin films (currents up to 5 A), using a two-axis goniometer which enables the user to rotate the sample about two mutually independent axes.
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Cryostat and electronics
SQUID magnetometers
A SQUID magnetometer utilizes a so-called superconducting quantum interference device, which is very sensitive to magnetic fields, for measuring the magnetic moment of a sample. Our group possesses two SQUID magnetometers, which facilitate examinations at temperatures ranging from 1.7 to 400 K, in magnetic fields of up to 7 T. We use these devices primarily for assessing the transition temperature and for measuring magnetization loops of superconductors. The latter under certain conditions allows an evaluation of the critical current density without performing a much more elaborate transport current measurement.
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Two commercial SQUID systems
Vector VSM
The Vector VSM (vibrating sample magnetometer) is capable of measuring both the parallel and the orthogonal component of the magnetic moment of a sample with respect to an applied magnetic field. The magnetic field with a maximum strength of 5 T is generated by a horizontally arranged superconducting magnet. The sample vibrates in the center of the magnet, and can be rotated about the vertical axis. The whole system is integrated in a gas flow cryostat, which provides temperatures ranging from 2.5 K to 350 K.
© Atominstitut, Photo: Michael Eisterer
5 T Vector VSM
Electromagnet
Our superconducting magnets are complemented by an ordinary electromagnet, whose advantage lies in easy handling: It does not require liquid helium, and samples can simply be placed inside a nitrogen Dewar between the pole shoes. The magnet can produce a maximum field of 1.6 T, whose angle relative to the sample can be adjusted by rotating the whole magnet.
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Electromagnet
Micro Hall scanner
Our micro Hall scanner measures local magnetic fields at the surface of superconductors with a resolution of 1 µm and a scanning area of 3 × 3 mm². This allows the investigation of magnetic granularity as well as the interplay of inter- and intra-granular currents. The micro Hall scanner is operated inside a cryostat, which contains an 8 T magnet and facilitates control of the sample temperature.
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Mikro-Hall-Scanner
Scanning Probe Microscope
Our group is in possession of a scanning probe microscope (SPM), in which a sample can be cooled to low temperatures (down to 4.2 K), and exposed to magnetic fields of up to 7 T. The SPM can be used in many acquisition modes such as atomic force (AFM), scanning tunneling (STM) or magnetic force microscope (MFM). The SPM can be used to examine the topography and the local magnetic properties of samples with a spatial resolution of less than 1 nm. The primary focus of the instrument is imaging of the magnetic flux line lattice of type-II superconductors.
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Scanning Probe Microscope
Hall scanner / Laser cutter
This device uses a Hall probe to measure local magnetic fields in close proximity to the surface of superconducting samples. We utilize it to examine high-temperature superconductors (primarily coated conductors), which are mounted inside a tub which is filled with liquid nitrogen during the measurement in order to cool the superconductor. The resolution of the scanner is significantly lower than that of the micro Hall scanner, but it offers a large scanning range of approximately 30 × 10 cm². In addition to the scan functionality, the system can be used to structure superconducting layers by means of laser cutting.
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Laser cutter
© Atominstitut, Photo: Michael Eisterer
Hall-Scanner
Optical digital microscope
The Keyence VHX-6000 digital microscope allows us to capture two- and three-dimensional images with a magnification of up to 5000x. In order to image large samples, the motorized XYZ table can be used to automatically combine many individual images into one large seamless image. The software supports length and thickness measurements as well as the determination of the surface roughness of samples. Using a polarization filter, crystal orientations on surfaces can be distinguished.
© Atominstitut
Optical digital microscope