55Mn NMR Study of the Field-Controlled Magnetic Phase Separation in (La0.25Pr0.75)0.7Ca0.3MnO3 with Different Oxygen Isotope Content

TL;DR

This study uses 55Mn NMR to investigate how oxygen isotope substitution influences magnetic phase separation and field-induced transitions in (La0.25Pr0.75)0.7Ca0.3MnO3, revealing controllable phase coexistence and magnetic ordering phenomena.

Contribution

It provides new insights into isotope effects on magnetic phase separation and demonstrates field-controlled manipulation of magnetic domains in manganites.

Findings

Magnetic phase separation occurs after field exposure above 5.3T.

FMM phase growth is controllable by external magnetic field.

Anomalous temperature dependence of nuclear relaxation rate observed.

Abstract

An influence of the 16O-18O isotope substitutions on magnetic state of perovskite-type manganite (La0.25Pr0.75)0.7Ca0.3MnO3 is studied by 55Mn NMR. Successive cycling with an isochronal exposure at different magnetic fields up to H=8T is used to study the field-induced transition from antiferromagnetic insulating (AFI) state to the ferromagnetic metal (FMM) one in the 18O-enriched sample. After exposure at H>H_{cr} \sim 5.3T the NMR spectrum of the 18O-sample evidences for magnetic phase separation (PS) resulted in the coexisting AFI and FMM domains. Further increase of exposing field leads to a progressive growth of the FMM phase at the expense of AFI domains. Its relative fraction can be controlled by external magnetic field and the resulting magnetic structure in the PS region is discussed. Anomalous T-dependence of the 55Mn nuclear spin-lattice relaxation rate is revealed in the FMM state of both 16O-and 18O-enriched samples. The manifestation of the Pr magnetic ordering at T \sim 40K is considered.