Instruments & Facilities
The sample preparation is the prerequisite for fundamental research of electronic and magnetic properties in polycrystalline materials, single crystals, thin films and nanoparticles.
- preparation of polycrystalline ceramics by surface reaction (mixed oxide)
- preparation of metallic alloys using a cold crucible
- preparation of oxidic and metallic single crystals with floating zone, Czochralski and solution growth
Contact: Jörg Persson
For the preparation of thin films the JCNS-2 has two high pressure sputter chambers and two oxide assisted molecular beam epitaxy (MBE) systems. One of the Oxide MBE mashines is stationed in Garching at the FRM II as a user facility. While in the Sputter chambers the material for the film growth is put in as a target with the right stoichiometry, in the Oxide MBE a stoichiometric growth is achieved by tuning the rates of the different element sources. The MBEs are equipped with RHEED, LEED and AES for in-situ characterization of the substrates and thin films. With the AES element resolved depth profiles can be obtained with the in-situ Argon ion gun. This ion gun can be used to structure the samples with 100µm resolution as well.
Due to the direct link between sample preparation and characterization with scattering methods and macroscopic probes, we have excellent opportunities for the variation of the important parameters for the function of the material under investigation.
In-House X-Ray Facilities
A series of instruments for the characterisation of samples using diffraction measurements are available in-house.
A reflectometer from Bruker AXS equipped with two Goebel mirrors before and after the sample allows for the fast characterisation of thin film samples.
Powder samples can be characterized in transmission geometry with a Huber Imaging Plate Guinier Camera G670 equipped with CuKα- or MoKα-radiation. The accessible temperature range reaches from 10 to 300 K using a closed-cycle cryostat and from 673 to 1773 K using a laser heating module.
Furthermore, two single crystal diffractometers are available. A large 4-circle Huber diffractometer with an Eulerian cradle operates at a standard CuKα source in combination with Goebel mirrors. An analyser crystal mounted before the scintillation counter warrants the measurement of highly resolved data. In addition, the beampath can be evacuated, so that an optimal peak-to-background ratio is achieved. The instrument is thus optimized for high resolution reciprocal space mapping, in particular on thin sections. A closed cycle He-cryostat (Advanced Research Systems) permits investigations in the temperature range from 300 K to 6.5 K.
The second single crystal diffractometer is a Supernova from Agilent Technologies and is equipped with switchable CuKα and MoKα microfocus sources and a CCD area detector for efficient data collection. It is mainly used for the measurement of diffraction intensities of single crystal samples for structure determination. A N2 cryostat and a Helijet from Oxford Instruments allow temperature dependent studies in the range from 490-90K and 90-10K, respectively.
MPMS, PPMS, CCMS:
JCNS-2 is equipped with two powerful state-of the-art instruments from Quantum Design, i.e. an MPMS-XL SQUID-magnetometer and a Physical Property Measurement System (PPMS). Both serve to characterize samples with respect to the following physical properties as function of both magnetic field and temperature:
- AC susceptibility
- Torque magnetometry
- Heat capacity
- Thermal transport properties
- Electrical transport properties
- Hall effect
- Seebeck coefficient
With the MPMS system one can measure the magnetization (or more precisely the magnetic moment) and the AC susceptibility at various applied magnetic fields between -7 and +7 T and temperatures between 1.9 and 400 K. One can program scans as function of field, temperature or time as automated sequences, e.g. hysteresis loops (see Figure below), ZFC/FC temperature measurements, magnetization relaxation curves, etc. The sensitivity is 10-8 emu. E.g. cobalt ultrathin films with a nominal thickness of 0.5 nm are routinely measurable. The samples should have a size not exceeding roughly 7mmx7mmx7mm and can be bulk crystals, thin films, nanoparticles, etc.
The PPMS system widens the possible methods to measurements of the heat capacity, thermal transport properties, electrical transport properties or the Seebeck coefficient in applied magnetic fields between -9 and 9 T and temperatures between 1.9 and 400 K. Furthermore, the magnetization and AC susceptibility can also be measured using the PPMS system although with a slightly lower sensitivity of ~10-6 emu compared to the MPMS system. In addition, the PPMS can also be used as a torque magnetometer, which provides information about magnetic anisotropies.
A third available system is the closed cycle measurement system (CCMS) built by Cryogenics Ltd (see Figure below). which provides a flexible measurement platform for magnetic fields up to 14 T in a temperature range between 1.6 and 325 K. The following standard options are available:
- VSM magnetometry
- AC susceptibility
- Hall effect
- Thermal conductivity
- Seebeck coefficient
Additionally, two specialized options are noteworthy: the AC-specific heat option for very small samples with a mass in the order of few µg, and the resonant ultrasound spectroscopy option that is used for the determination of elastic constants and speed of sound. Measurements are usually fully automatized.