Persistent ferromagnetism in antiferromagneticPr0.6Ca0.4MnO3

Abstract

We report on the magnetic-field-driven persistent ferromagnetic (FM) state in antiferromagnetic (AF) manganite ${\text{Pr}}_{1\ensuremath{-}x}{\text{Ca}}_{x}{\text{MnO}}_{3}$, where $x=0.4$ and 0.375. At low temperatures the magnetic field-induced ferromagnetism (FIFM) persists even at $B=0$ and is quenched to a fractional value of the total number of spins. This incomplete ferromagnetism decreases with increasing temperature and disappears at ${T}_{m}=10--20\text{ }\text{K}$. ${T}_{m}$ depends on the hole concentration ``$x$'' and increases as $x\ensuremath{\rightarrow}0.3$. We interpret this as the incomplete relaxation from FM toward AF spin orientation, resulting in the canted antiferromagnetism (CAF). This is in contrast to the ``virgin'' (zero-field cooled) magnetic ground state where no ferromagnetic component could be detected. Due to the strong competition between FM and AF orders, three successive AF transitions are detected. The low-temperature transition at ${T}_{3}=27\text{ }\text{K}$ has a strong influence on FIFM, resulting in the minimum magnetic field required to trigger the FIFM state. Furthermore, the ${T}_{3}=27\text{ }\text{K}$ transition results in a pronounced anomaly in the temperature variation in magnetization. We comment on this property in the light of a similar finding in the phase-separated ${\text{La}}_{0.21}{\text{Pr}}_{0.42}{\text{Ca}}_{3/8}{\text{MnO}}_{3}$ which was interpreted as the strain-glass transition.