The DynaCool PPMS is designed to measure the physical properties of materials in bulk, thin film, and powder form, provided samples thereof are sufficiently small to fit within the measurement volume of the instrument. Electrical transport measurements, for example, are typically limited to samples having a lateral extent less than 10 mm x 10 mm and a thickness of several millimeters. Magnetometry, on the other hand, limits the diametrical extent of a sample to less than 4.5 mm and its length to several millimeters. Powders are typically pressed into geometries (sometimes with the aid of binders) that satisfy these dimensional requirements. The currently available measurement options are DC resistivity, electrical transport, a multi-function probe, and vibrating sample magnetometry (VSM).
DC resistivity can be either 2- or 4-wire, and when in 4-wire mode, the mode greatly reduces the contributions from lead and contacts resistances. Within the approximately 10 mm x 10 mm mounting area within the instrument, there is typically room for up to 3 samples, provided they are sized appropriately.
The electrical transport option (ETO) also supports 2- or 4-wire mode, and again, 4-wire mode is advantageous in terms of reducing the contribution of lead and contact resistances. With proper lead placement, however, the Hall coefficient also can be measured in 4-wire mode. In addition to resistance (and Hall coefficient), 2- and 4-wire current-voltage curves as well as differential resistance (dV/dI) can be measured. Whereas the voltage response is measured in response to a current excitation in 4-wire mode, current response is measured in response to a voltage excitation. In contrast to the resistance option, only 2 samples are supported within the approximately 10 mm x 10 mm measurement area when the ETO is used.
The VSM option is a fast, sensitive, and fully automated DC magnetometer. This measurement is accomplished by oscillating the sample in a pickup coil and synchronously detecting the induced voltage. By using a compact gradiometer pickup coil configuration, a relatively large oscillation amplitude (1-3 mm peak), and a frequency of 40 Hz, the system can resolve magnetization changes of less than 10-6 emu at a data rate of 1 Hz. Due to the size of the pickup coil, samples are currently limited to diameters and lengths of less than 4.5 mm and 5 mm, respectively. Whereas the diameter is physically limited by the bore of the pickup coil, lengths in excess of 5 mm tend to produce a reduced moment that is best to avoid. Samples are mounted to either quartz paddles or brass troughs, as required.
Lastly, the multifunction probe option is a sample mounting platform that contains a calibrated thermometer and direct axial ports that may be used for light pipes, fiber optics, extra leads, waveguides, and so on. It has the same restrictions on sample size and the ETO, but unlike the ETO, the angle of the platform can be changed so that the field and sample normal can be at angles other than 90 degrees.
Specifications
- Cryogen-free, 2.5 cm clear bore, with integrated high vacuum (10-4 Torr)
- Highly stable (±0.1% for T < 20 K, ±0.02% for T > 20 K) temperature from 1.8 to 400 K
- Continuous low temperature control and temperature sweep modes
- Highly uniform (±0.01% over 3 cm) longitudinal field (± 9 T)
- Linear, oscillating, and no overshoot modes
Options currently available:
- Vibrating Sample Magnetometer (VSM)
- rms sensitivity < 10-6 emu with 1 second averaging
- Multifunction probe with calibrated thermometer and direct axial ports (for fiber optics, extra leads, etc.)
- DC resistivity
- 4 independent channels
- Current drive from 2 nA to 8 mA
- Resistances up to 5 GΩ
- Electrical transport (for AC resistance, Hall effect, I-V, and differential resistance measurements)
- 2 independent channels
- 1 nV sensitivity, 10 nΩ resolution at 100 mA
- AC and DC drive amplitudes from 10 nA to 100 mA
- Resistances from 10 µΩ to 5 GΩ
