The main aim of the present work is to study the synthesis and stability of soft-magnetic nanostructured materials under high pressure - high temperature conditions. NANOPERM alloy powders were prepared by high-energy ball-milling. The as-milled alloys consist of a iron-based nanocrystalline solid solution. The evolution of crystallinity and grain-size during the ball-milling process and investigations under external pressure up to 3 GPa for temperatures up to 1200°C were evaluated using synchrotron radiation X-ray diffraction. The X-ray experiments were performed at the B2/MAX80 instrument beamlines at DESY/HASYLAB, Hamburg, Germany.