Abstract
Monovalent doped Pr0.75Na0.25-yAgyMnO3 (y = 0–0.10) manganite have been investigated using X-ray diffraction (XRD) and scanning electron microscope (SEM) as well as DC electrical resistivity and AC susceptibility measurement to clarify the influence of Ag- doped on charge ordering (CO) state. XRD analysis revealed all samples consists of essentially single phase and crystallized in an orthorhombic structure with space group Pnma. SEM images of Pr0.75Na0.25-yAgyMnO3 compound shows the successful substitution of Ag+ ions with the enhancement of the grains boundaries and sizes as well as the compaction of particles. On the other hand, resistivity and susceptibility measurements showed that the y = 0 sample exhibits insulating behavior and anti-ferromagnetic. Interestingly, the ferromagnetic-metallic transition was observed for y = 0.05 due to the revival of double-exchange (DE) mechanism as a result of weakening the Jahn-Teller effect which caused the CO state to be weakened. However, increasing of Ag-doped up to y = 0.10 induce back its transition into anti-ferromagnetic insulating behavior suggestively due to the weakening of DE mechanism.
Highlights
This Hole-doped perovskite manganites with the general formula Re1-xAxMnO3 where Re is trivalent rare-earth ion (Pr3+, La3+, Nd3+, Dy3+) and A is divalent (Ca2+, Sr2+, Cr2+) or monovalent (Ag+, K+, Na+) alkaline earth ions have received remarkable attention since discovery the Colossal Magnetoresistance (CMR) effect due to their unique magnetic and transport properties as well as the potential application at low temperature [1,2]. These behaviors can be associated with the double exchange (DE) interaction involving the exchange of Mn3+ with Mn4+ which favor the ferromagnetic metallic (FMM) state [3] and Jahn Teller interaction that dominated the Mn3+ ion causing the behavior of paramagnetic insulating (PMI) [4] as well as charge ordering (CO) state
X-ray diffraction (XRD) analysis revealed all samples were in single phase and the crystal structure was indexed as an orthorhombic perovskite-structured whose unit cell belongs to the space group Pnma reliable with the previous study that reported the structure [16, 17]
The increasing in values of density (D), as well as decrease in porosity with Ag content, shows a good agreement with the changing of unit cell volume (V) indicating a successful substitution of Ag+ ions in the system
Summary
This Hole-doped perovskite manganites with the general formula Re1-xAxMnO3 where Re is trivalent rare-earth ion (Pr3+, La3+, Nd3+, Dy3+) and A is divalent (Ca2+, Sr2+, Cr2+) or monovalent (Ag+, K+, Na+) alkaline earth ions have received remarkable attention since discovery the Colossal Magnetoresistance (CMR) effect due to their unique magnetic and transport properties as well as the potential application at low temperature [1,2]. Substitutions of K+ ions at A-site of Pr0.75Na0.25-xKxMnO3 shows the interesting phenomena where the increment of K+ ions suppress the CO state as well as induce the ferromagnetic-metallic transition at lower temperature with increasing of TC and TMI due to the reduction in MnO6 octahedral distortion enhanced double exchange (DE)
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