  e report the effect of pressure on the steplike magnetostriction of single
crystalline bilayered manganite (LaPr)1.2Sr1.8Mn2O8, for our understandings of
the ultrasharp nature of the field-induced first-order transition from a
paramagnetic insulator to a ferromagnetic metal phase. The application of
pressure suppresses a steplike transformation and causes a broad change in the
magnetostriction. The injection of an electric current to the crystal also
weakens the steplike variation in both the magnetostriction and
magnetoresistance. The stabilization of ferromagnetic interaction or the
delocalization of charge carriers is promoted with the applied pressure or
applied current, resulting in the suppressed steplike behavior. Our findings
suggest that the step phenomenon is closely related to the existence of
localized carriers such as the short-range charge-orbital ordered clusters.
