Modulated magnetism in metallic ferromagnets close to quantum criticality

We demonstrate that strong electronic particle-hole fluctuations near to an avoided ferromagnetic quantum critical point give rise to the formation of helimagnetic order. In the presence of small magnetic anisotropy it is possible to tune through this phase reconstruction by small transverse magnetic field and to stabilise a modulated fan state in between the homogeneous ferromagnetic phase and the field polarised state. We show that our theory can explain the rich behaviours observed in the metallic ferromagnetic PrPtAl.