High entropy effect on double exchange interaction and charge ordering in half doped Nd0.5Sr0.5MnO3 manganite

The entropy stabilized oxides i.e., the so-called high-entropy oxides are of great interest in recent time due to their intriguing physical properties. This new category of advanced materials is stabilized by the high configurational entropy of randomly mixed elements, where a specific lattice site is populated by five or more elements. The present study is devoted to explore the high entropy effect in well-known charge ordered manganite Nd0.5Sr0.5MnO3 where a delicate balance exists between the ferromagnetic double exchange and the antiferromagnetic superexchange interactions. Powder X-ray diffraction analyses confirm phase purity of the samples. FE-SEM imaging revealed the microstructure and elemental mapping con-firmed the chemical homogeneity of the samples as well as nominal cationic composition. Bond valence sum (BVS) calculation using refinement parameters supports the expected cationic valence in all the samples. Replacement of Nd3+ by five trivalent cations as in (La0.1Pr0.1Nd0.1Gd0.1Bi0.1)Sr0.5MnO3 with larger average A-site ionic radius, < rA > and smaller size variance, sigma 2 compared with Nd0.5Sr0.5MnO3 dramatically suppressed the ferromagnetic double exchange interaction. This observation is in contrast with the ex-pected variation in < rA> and sigma 2. In (La0.1Nd0.1Gd0.1Bi0.1Y0.1)Sr0.5MnO3 with smaller < rA> and marginally higher sigma 2 the ferromagnetic state ceases to exist. In both the multicationic compositions, a long-range antiferromagnetic state is evolved around 200 K with the retention of charge ordering. In the high entropy (La1/6Nd1/6Dy1/6Ca1/6Ba1/6Sr1/6)MnO3 composition with nominal < rA> and larger sigma 2 values the high tem-perature long-range ordering is completely suppressed and a new antiferromagnetic state is evolved at 45 K without manifestation of any charge ordering. This composition also avoids magnetic frustration unlike the dopant variant with larger sigma 2. The present investigation thus highlights the role of local lattice distortion or high entropy effect apart from the < rA > and sigma 2 in manganites. (c) 2023 Elsevier B.V. All rights reserved.

Automated summary

In recent years, there has been great interest in the entropy stabilized oxides, known as high-entropy oxides, due to their intriguing physical properties. This study focuses on exploring the high entropy effect in the charge ordered manganite Nd0.5Sr0.5MnO3, where the balance between ferromagnetic double exchange and antiferromagnetic superexchange interactions is delicate. The results show that the substitution of Nd3+ with five trivalent cations dramatically suppresses the ferromagnetic interaction, contrary to the expected variation in ionic radius and size variance. Furthermore, different multicationic compositions exhibit the emergence of long-range antiferromagnetic states with retained charge ordering. The investigation highlights the role of local lattice distortion or high entropy effect in manganites, in addition to ionic radius and size variance.