Pressure-Induced Inhomogeneous Chiral-Spin Ground State in FeGe

Fe-57 nuclear forward scattering on the chiral magnet FeGe reveals an extremely large precursor phase region above the helimagnetic ordering temperature T-C(p) and beyond the pressure-induced quantum phase transition at 19 GPa. The decrease of the magnetic hyperfine field < B-hf > with pressure is accompanied by a large increase of the width of the distribution of < B-hf >, indicating a strong quasistatic inhomogeneity of the magnetic states in the precursor region. Hyperfine fields of the order of 4 T (equivalent to a magnetic moment mu(Fe) approximate to 0.4 mu(B)) persist up to 28.5 GPa. No signatures of magnetic order have been found at about 31 GPa. The results, supported by ab initio calculations, suggest that chiral magnetic precursor phenomena, such as an inhomogeneous chiral-spin state, are vastly enlarged due to increasing spin fluctuations as FeGe is tuned to its quantum phase transition.