Physical Property Measurement System

Remember our MPMS?



The venerable Magnetic Property Measurement System from Quantum Design, set up at our university in 1996. This then is the partial replacement, a PPMS DynaCool from the same manufacturer. Apparently only the second device of this configuration in all of Germany. It was turned on for the first time yesterday and performed its initial cooldown to liquid helium temperature, being ready for the first instruction session today. In contrast to our old machine, this doesn't need to be refilled with liquid helium twice per week (or more) because it's a cryogen-free design. It does still use liquid helium as coolant, but it's able to produce it by itself, with a built-in pulse tube cooler. All you need is a high pressure gas bottle of helium, which should be good for three months, according to the manufacturer.

Unlike our system, which is aimed specifically at magnetic measurements, this beast is an all-purpose machine, capable of a large number of measurement options which can often be customized to fit your need. Our group is mainly interested in the VSM option, the vibrating sample magnetometer, which allows much faster measurements than our machine, with the built in magnet being able to apply a field of 9 Tesla, four more than our machine. However, because it's not an explicit magnetometer, the sensitivity is lower by one magnitude. This should still be more than enough for just about any task, but on paper, our old machine still has the edge in terms of sensitivity. The new one also lacks an option for direct measurements of the magnetic susceptibility via alternating fields, something that makes our device very desirable for measurements on nanoparticles, and for our custom-built magnetoeletric setup.

The biggest disadvantage though: Our group is only eligible for one day per week of measurement time, as our share of the proposal was only 15% of overall usage. In contrast to this, we outright own the old device, thus being able to measure what we want, when we want. A big advantage if you ask me. So despite the new device being all shiny, fancy, and not requiring me to push around huge dewar flasks with liquid helium, the old one will probably remain in full service for a few more years to come.