Influence of A-site disorder on the half-doped manganites

Abstract

The electronic transport and magnetism in half-doped Nd0.50Ca0.25Sr0.25MnO3 manganites have been investigated. Contrary to general half-doped system, it only displays a paramagnetic-ferromagnetic phase transition associated with an insulator-metal transition instead of with any features of charge ordering. With the decrease of temperature, an electronic phase separation and spin glass state occur in low temperature. We suggest that the A-site cation disorder induced by the size mismatch between Sr2+ ion and Ca2+ ion is mainly responsible for this phenomenon.

Charge ordering phase submerged in ferromagnetic ordering phase in the Nd 0.5 Sr 0.5 MnO 3 system

“…It should be noted that for all doped samples, an inflexion in ρ-T curves is observed at the semiconductorlike region, which is a characteristic for the existence of the CO phase [19]. This property is consistent with that reported in the Nd 0.5 Ca 0.5 MnO 3 system [18,20]. The temperature corresponding to the inflexion in the ρ-T curves is defined as T CO .…”

Heisenberg-like ferromagnetism and percolative conductivity in the half-doped manganite Nd0.5Ca0.25Sr0.25MnO3

“…However, in the present materials, these characters have not been observed. In our previous investigation [14], we have suggested that the A-site cation disorder induced by the size mismatch between Sr 2 + ion and Ca 2 + ion was mainly responsible for this phenomenon. However, for further understanding the above behavior, two important questions about PM-FM transition should be firstly considered: one is the order of phase transition, the other is the common universality class.…”

“…The detailed experimental process has been reported in Ref. [14]. The Powder X-ray diffraction was employed on Japan Rigaku D/max-ga rotating powder diffractometer using Cu Ka radiation to check the structure and phase purity.…”

“…A few percent substitutions of Cr easily destroy the long-range CO phase and induce the ferromagnetic phase locally, which results in the phase separated ground state with both CO and FM clusters randomly distributed [11][12][13]. However, our recent research shows that the paramagnetism-ferromagnetism (PM-FM) transition and insulator-metal (IM) transition are observed in the half-doped manganite Nd 0.5 Sr 0.25 Ca 0.25 MnO 3 [14]. Due to the large mismatch of ionic size between Ca 2+ and Sr 2+ (r Ca ¼1.18Å, r Sr ¼1.31Å), a considerable disorder on A-site causes inhomogeneous strain field so that it is impossible to form a long-rang CO phase.…”