The longitudinal and transverse magnetoresistance curves MR(H) and the magnetization
isotherms M(H) were measured at T = 3 K and 300 K up to high magnetic fields for a
microcrystalline (µc) Ni foil with grain sizes above 1 µm (corresponding to bulk Ni)
and for a nanocrystalline (nc) Ni foil with an average grain size of about 100 nm.
At T = 3 K, the field-induced resistivity change was quite different for the two microstructural
states of Ni and the evolution of resistivity with magnetic field was also different
which could be explained as arising from their very different electron mean free paths.
At T = 300 K, the MR(H) curves of both the μc-Ni and nc-Ni samples were very similar
to those known for bulk Ni. The MR(H) data were analyzed at both temperatures with
the help of Kohler plots from which the resistivity anisotropy splitting (ΔρAMR) and
the anisotropic magnetoresistance (AMR) ratio were derived, the latter values being
very similar at both temperatures and for both microstructural states of Ni metal.
The present high-precision MR(H) data revealed that the available theoretical models
do not accurately describe the suppression of thermally induced magnetic disorder
at around room temperature in high magnetic fields.
