Aim: Learning how to quantify magnetic exchange interactions. Side aim: Introducing the class of 2D "correlated van-der-Waals materials".

• Calder et al., Phys. Rev. Lett. 2019

Guiding questions:

• Which material is studied and why it is relevant?
• Why is Ref. 21 of Calder's paper important? Spoiler: The Mermin-Wagner theorem implies absence of long range magnetic order in a 2D isotropic Heisenberg system at finite temperature. What does this statement imply for the Fe3GeTe2 sytem under study?
• How does the time-of-flight INS experiment work?
• Explain the results of the experiment.