[en] A laser plasma accelerator is under development at the Max-Planck-Institut fuer Quantenoptik in Garching. This accelerator will be part of an X-ray table top FEL in the future. The FEL radiation will be produced with a small period in-vacuum undulator. The coercivity of the magnetic material has to be sufficiently high in order to avoid demagnetization due to electron losses. The best performance can be achieved with a cryogenic permanent magnet undulator design. (Nd_0.2Pr_0.8)₂Fe₁₄B magnets are suited for low temperatures since they do not suffer from a spin reorientation. A new (Nd_0.2Pr_0.8)₂Fe₁₄B material has been characterized at various temperatures and the results are presented. Based on this material a 20 period prototype with a period length of 9 mm and a magnetic gap of 2.5 mm is currently under construction.