  We have recently established that a number of Dzyaloshinskii-Moriya
interaction driven canted antiferromagnets or weak ferrromagnets (WFM)
including hematite exhibit an ultra-slow magnetization relaxation phenomenon,
leading to the observation of a time-stable remanence (Phys. Rev. B 96, 104422
(2017)). In this work, our endeavor is to optimize the magnitude of this
time-stable remanence for the hematite crystallites, as a function of shape
size and morphology. A substantial enhancement in the magnitude of this unique
remanence is observed in porous hematite, consisting of ultra-small nano
particles, as compared to crystallites grown in regular morphology, such as
cuboids or hexagonal plates. This time-stable remanence exhibits a peak-like
pattern with magnetic field, which is significantly sharper in porous sample.
The extent and the magnitude of the spin canting associated with the WFM phase
can be best gauged by the presence of this remanence and its unusual magnetic
field dependence. Temperature variation of lattice parameters bring out
correlations between strain effects that alter the bond length and bond angle
associated with primary super exchange paths, which in-turn systematically
alter the magnitude of the time-stable remanence. This study provides insights
regarding a long standing problems of anomalies in the magnitude of
magnetization on repeated cooling in case of hematite. Our data caps on these
anomalies, which we argue, arise due to spontaneous spin canting associated
with WFM phase. Our results also elucidate on why thermal cycling protocols
during bulk magnetization measurements are even more crucial for hematite which
exhibits both canted as well as pure antiferromgnetic phase.
