Dopant-Dependent Impact of Mn-Site Doping on Critical-State Manganites R_0.6Sr_0.4MnO₃ (R=La, Nd, Sm, and Gd)

Abstract

Versatile features of impurity doping effects on perovskite manganites, R 0:6 Sr 0:4 MnO 3 , have been investigated by varying the doping species as well as the R-dependent one-electron bandwidth in the single-crystalline specimens. In ferromagnetic-metallic (FM) manganites (R ¼ La, Nd, and Sm), a few percent of Fe substitution dramatically decreases the ferromagnetic transition temperature, leading to a spin glass insulating (SGI) phase for each R species. There, the correlation of charge-orbital ordering in competition with metallic ferromagnetism is effectively induced, which has been observed as an evolution of diffuse electron scattering even in the R ¼ La system with the largest bandwidth. Such a marked impact of Fe doping, widely observed in a variety of FM manganites, virtually results in the reduction in the bandwidth for the system in the critical region near the SGI phase. We have also found a contrastive impact of Cr (or Ru) doping on a SGI manganite (R ¼ Gd). For these dopants, the impurityinduced ferromagnetic magnetization is observed at low temperatures as a consequence of the collapse of the inherent short-range charge-orbital ordering, whereas Fe doping gives only a minimal influence. Thus, the opposite nature of Fe and Cr doping tends to generally hold for bicritical-state manganites with various bandwidths and phase correlation lengths. This may stem from the difference in magnitude of the antiferromagnetic interactions between the Fe-Fe and Cr-Cr couplings.

Competing A‐site and B‐site doping effects on magneto‐transport of RE0.55 Sr0.45 Mn1−x Rux O3 manganites in the vicinity of the SGI and FMM border

“…1g-i). A similar decrease of the magnetization and/or in-phase ac susceptibility has been observed in B-site doped single crystal of Gd 0.6 Sr 0.4 MnO 3 manganites [14]. These transitions may be caused by the formation of the spin-glass phase.…”

Magnetic reconstructions in B-site doped manganites

“…A colossal response in a magnetic field emerges due to the A-site disorder which promotes phase coexistence and metalinsulator transition 8,9 . Similar phase coexistence scenario have also been observed in B-site doped manganites RE 1−x AE x Mn 1−η B η O 3 where a few percentage of Mn-sites are replaced by foreign elements named B-site dopants [10][11][12][13][14][15][16][17][18][19][20] . In addition, the B-site disorder can tune a ferromagnetic (FM) metal to an anti-ferromagnetic (AF) insulator 16,18 or vice-versa 11 .…”

“…Similar phase coexistence scenario have also been observed in B-site doped manganites RE 1−x AE x Mn 1−η B η O 3 where a few percentage of Mn-sites are replaced by foreign elements named B-site dopants [10][11][12][13][14][15][16][17][18][19][20] . In addition, the B-site disorder can tune a ferromagnetic (FM) metal to an anti-ferromagnetic (AF) insulator 16,18 or vice-versa 11 . This promotion of a competing ordered phase has no equivalent in the case of A-site disorder.…”

Impact of Bicritical Fluctuation on Magnetocaloric Phenomena in Perovskite Manganites

“…Single crystals of R 0.6 Sr 0.4 MnO 3 (R=La-Gd) were grown by a floating zone method. 12,13 Powder x-ray diffraction exhibited that the obtained crystals are of single phase. The magnetization was measured with a superconducting quantum interference device (Quantum Design).…”