Magnetic and transport properties of La0.7Sr0.3Co1−yMnyO3—No double exchange between Mn and Co

Effect of Co doping on the magnetic properties of La0.85Ag0.15(Mn1−yCoy)O3

“…The increase in T c for y40.20 could be due to DE FM interactions in Co 3+ -O 2À -Co 4+ networks. Similar behavior was observed by Phuc et al [17] in cobalites La 0.70 Sr 0.30 Co 1Ày Mn y O 3 .…”

Observation of mixed-phase behavior in the Mn-doped cobaltite La0.7Sr0.3Co1−xMnxO3 (x=0–0.5)

“…Magnetic and transport properties of Co-doped La 0.7 Sr 0.3 MnO 3 were previously reported by several other authors [1,2]. Recently, we also have found that, while both La 0.7 Sr 0.3 MnO 3 and La 0.7 Sr 0.3 CoO 3 are double-exchange (DE) ferromagnets, the interaction between Mn and Co ions in fact is superexchange antiferromagnetic (AF), as observed in La 0.7 Sr 0.3 Co 1 À x Mn x O 3 [3,4]. A substitution of only 10% of Co ions by Mn totally suppresses the ferromagnetism and metallic conductivity, turning the system into an insulating spin glass (SG) [3].…”

“…Recently, we also have found that, while both La 0.7 Sr 0.3 MnO 3 and La 0.7 Sr 0.3 CoO 3 are double-exchange (DE) ferromagnets, the interaction between Mn and Co ions in fact is superexchange antiferromagnetic (AF), as observed in La 0.7 Sr 0.3 Co 1 À x Mn x O 3 [3,4]. A substitution of only 10% of Co ions by Mn totally suppresses the ferromagnetism and metallic conductivity, turning the system into an insulating spin glass (SG) [3]. Higher Mn substitution (x40.2) leads to a recovery of ferromagnetism due to DE interaction between Mn ions but, surprisingly, not metallic conductivity (at least up to x = 0.5).…”

Non-uniform behavior of La0.7Sr0.3Co1−Mn O3 (y=0.3 and 0.5) compounds

“…Besides, the issue of Co ions in different spin states is also at the focus of much current research. In a previous paper [2], we have evidenced that there exists no double exchange between Co and Mn in the La 0.7 Sr 0.3 Co 1Ày Mn y O 3 compounds, and also a sign of changing towards higher spin states of the Co ions with increasing Mn concentration. This paper, which to some extent overviews the previous work, focuses primarily on the y ¼ 0:3 and 0.5 compounds, whose properties are not in conformity with the DE mechanism.…”

“…Below 25 K, the M s and w p values could not be extracted, because the MðHÞ curves, instead of showing a well-determined high-field linear region, have S-shape characteristics. In a previous work [2], we have argued that conversions to higher-spin states of the Co ions are favored by the Mn substitution. Assuming that, for y ¼ 0:3; all of the Co and Mn ions are in high-spin states and that the ionic concentration ratios Co 3+ /Co 4+ and Mn 3+ /Mn 4+ are maintained at 7/3, we expect a zero-temperature saturation magnetization as high as B100.4 emu/g.…”