Revealing defect-induced spin disorder in nanocrystalline Ni

We combine magnetometry and magnetic small-angle neutron scattering to study the influence of microstructure on macroscopic properties a nanocrystalline Ni bulk sample, which was prepared by straining via high-pressure torsion (HPT). As seen magnetometry, mechanical deformation leads significant increase coercivity compared with nondeformed polycrystalline Ni. The data reveal spin-misalignment caused high density crystal defects inside were created severe plastic during sample preparation. corresponding correlation length, characterizes spatial magnetization fluctuations in real space, indicates an average defect size 11 nm, is smaller than crystallite 60 nm. In remanent state, strain fields around cause spin disorder surrounding ferromagnetic bulk, penetration depth \ensuremath{\sim}22 range amplitude systematically suppressed increasing external field. Our findings are supported illustrated micromagnetic simulations, for case nonmagnetic (holes) embedded phase, further highlight role localized perturbations defect-rich magnets such as HPT materials.