Steplike lattice deformation of single crystalline (La0.4Pr0.6)1.2Sr1.8Mn2O7 bilayered manganite

We report a steplike lattice transformation of single crystalline (La0.4Pr0.6)(1.2)Sr1.8Mn2O7 bilayered manganite accompanied by both magnetization and magnetoresistive jumps, and examine the ultrasharp nature of the field-induced first-order transition from a paramagnetic insulator to a ferromagnetic metal phase accompanied by a huge decrease in resistance. Our findings support that the abrupt magnetostriction is closely related to an orbital frustration existing in the inhomogeneous paramagnetic insulating phase rather than a martensitic scenario between competing two phases.