Tuning Magnetic Interaction by Cr Substitution in Pr-Based Pr0.75na0.05k0.20mn1- X Cr X O3 (X = 0 - 0.05) Monovalent Doped Manganites

Abstract

This study investigated the effects of Cr3+ on the structural and magnetic properties of Pr0.75Na0.05K0.2Mn1-xCrxO3 (x = 0.0, 0.01, 0.02, 0.03, 0.04, 0.05) synthesised using the solid-state method. An analysis of room temperature X-ray diffraction data using the Rietveld refinement method showed all samples crystallised in the orthorhombic phase with Pnma space group. It is found that unit cell volume increased from 230.60 A3 (x = 0) to 231.25 A3 (x = 0.01) suggesting that substitution with a low concentration of Cr3+ may predominately substitute for Mn4+ site. However, by further substituting Cr3+ caused a decrease in unit cell volume from 231.15 A3 (x = 0.02) to 227.74 A3 (x = 0.05), indicating a high concentration of Cr3+ dominantly substituted the Mn3+. Cr3+ substitution slightly decreased the [[EQUATION]] value from 140.7 K (x = 0.00) to 139.7 K (x = 0.01) and 139.3 K (x = 0.02) indicates the substitution of Cr3+ weakened ferromagnetic (FM) interaction between Mn3+-O2--Mn4+ which may be related to the dominant effect of the decrease of Mn3+/Mn4+ ratio as Cr3+ replaced Mn4+. However, the further substitution of Cr3+ increased the [[EQUATION]] to 140 K (x = 0.03), 140.7 K (x = 0.04) and 143.4 K (x = 0.05) samples, indicates that Cr3+ enhanced the ferromagnetic interaction. The enhancement of ferromagnetic interaction may arise due to a combination of ferromagnetic interaction between Mn3+-O2--Mn4+ and Cr3+-O2-Mn3+, thus weakening the antiferromagnetic (AFM) interaction between Cr3+-O2--Cr3+ and Cr3+-O2- -Mn4+. These findings revealed the possibility of the existence of ferromagnetic interaction between Cr3+ and Mn3+ ions due to the similar electronic configuration of Cr3+ with that of Mn4+ ions. The variation in the observed magnetic properties indicates that the Cr3+ substituted samples are considerably suitable for further investigation for spintronic-based device materials.

Keywords: Perovskite manganite, Cr-substitution, X-ray photoelectron spectroscopy, Magnetic properties, griffith phase