•The magnetic studies have been carried out on the R-doped La0.5Ba0.5Co0.9R0.1O3.•Cr3+ gives an extraordinary effect of enhancing TC a lot among all these doping ions.•The electron spin resonance spectra confirm the Co-O-Cr exchange interaction.•The magnetotransport implies a double-exchange property of this interaction.The magnetic studies have been carried out on the R-doped La0.5Ba0.5Co0.9R0.1O3 (R = Cu, Zn, Cr, Ni, Ti and Ru) cobaltites. X-ray absorption near-edge structure (XANES) proves these ions are in the valence state of Cu2+, Zn2+, Cr3+, Ni3+, Ti4+ and Ru4+. Magnetic moment calculation shows both Co3+ and Co4+ hold in the intermediate spin state. Based on the ratio of Co3+/Co4+, the average B-site size, the tolerance factor and electron itinerancy, the different influence of these ions on the magnetism were discussed. Among all these ions, Cr3+ gives an extraordinary effect of enhancing TC a lot. It is attributed to the Co-O-Cr exchange interaction, which is confirmed by the electron spin resonance spectra. The typical magnetotransport behavior implies a double-exchange property of this exchange interaction.

Polycrystalline samples of Ba-doped Bi0.5Sr0.5MnO3 have been prepared by a standard solid-state reaction. The influence of the Ba doping effect on the structural, macro-magnetic, and micro-magnetic properties of the compounds has been investigated experimentally. All the samples crystallize in an orthorhombic structure and the lattice parameters increase continuously with increasing Ba doping level. Due to the increase of the egeg electron bandwidth resulting from the Ba doping, the charge-ordering (CO) transition temperature TCO decreases noticeably. Both the macro-magnetic and the micro-magnetic data show that, in all the samples, only a paramagnetic (PM)/charge-disordered state exists above the CO transition, and only a charge-ordered state coexists with the PM matrix below the CO transition, while an antiferromagnetic (AFM) state coexists with a ferromagnetic (FM) state and a paramagnetic (PM) state at temperatures below the Néel temperature (TN).Highlights► Polycrystalline Ba-doped Bi0.5Sr0.5MnO3 samples have been prepared by a standard solid-state reaction. ► The Ba doping effect on the structural, macro-magnetic, and micro-magnetic properties of the compounds has been investigated. ► Due to the increase of the egeg electron bandwidth, TCO decreases noticeably. ► Multiple phases coexist in the compounds.

The isospinel structural compounds CuIr2−xMxS4 (M=W/Mn) are designed to study the different influences on the 5d5d electrons of Ir. W ions acting as W4+ in CuIr2−xWxS4, while Mn ions act as Mn2+ in CuIr2−xMnxS4. The suppression of W4+ on the Peierls-like phase transition is more effective than that of Mn2+. The influences of W4+ and Mn2+ on the magnetization are different. The doping of W4+ causes diamagnetism even before the Peierls-like phase transition in CuIr2−xWxS4 system, while Mn2+ produces a paramagnetic background in the CuIr2−xMnxS4 system.

The magnetic properties of Y 0.35Ln0.05Ca0.6MnO3 (Ln = La, Pr, Nd, Sm, Gd, Dy) have been investigated thoroughly. The small average cationic radius 〈rA〉〈rA〉 of the present system results in a short-range antiferromagnetic charge-ordering (AFM-CO) state in the manganites. With the decrease of temperature, a super-exchange interaction begins to establish itself between the remaining disordered Mn ions after the formation of the short-range CO state. Then, the reentrant cluster-glass state originates from the frustration between the FM order in the clusters and the AFM interactions present in the background matrix. However, the large magnetic moments of Gd3+ and Dy3+ ions apply an internal magnetic field on the Mn3+ and Mn4+ ions, which results in the suppression of the cluster-glass state.

The magnetic properties of Nd0.6Ln0.1Sr0.3MnO3 compositions (Ln = La, Pr, Gd, Dy) have been investigated thoroughly. The effect of 〈rA〉〈rA〉 is considered to be profound on the PM–FM phase transition in the manganites. The experiment results indicate that TCTC decreases with Ln changing from La to Gd due to the decreases of 〈rA〉〈rA〉. The abnormal increase of TCTC in Dy-composition with the smallest 〈rA〉〈rA〉 and largest σ2σ2 is attributed to the large magnetic moment of Dy3+ ions. The rapid increase of magnetization below 30 K indicates directly the magnetic ordering of rare earth ions at A-site.

The structural, magnetic, and transport properties of the polycrystalline-doped systems Nd0.7Sr0.3Mn1−xGaxO3 (0≤x≤0.200≤x≤0.20) were investigated. For the parent and low-doped samples (0≤x≤0.110≤x≤0.11), they show a long-range ferromagnetic state below TCTC and the Griffiths singularity above TCTC. When xx further exceeds 0.12, a transition from the metal ferromagnetic to the insulating cluster-spin-glass state as a function of Ga doping takes places at low temperatures. x=0.12x=0.12 is just a critical point xcxc transforming from the Griffiths singularity to the cluster-spin-glass state.

In order to experimentally probe the complicated interaction between charge ordering and spin ordering in manganites, two sets of samples Ca0.875Ce0.125Mn1−xCrxO3 and Ca0.875Ce0.125Mn1−yGayO3 (0.0≤x,y≤0.0750.0≤x,y≤0.075) have been studied by means of electrical transport measurements, magnetization measurements and electron spin resonance. A large difference between the evolution of the charge ordering temperature Tco in the Cr doping and the Ga doping cases is found. For Cr-doped samples, the Tco decreases to 150 K at x=0.025x=0.025 and then disappears when xx exceeds 0.05. But in Ga-doped samples, although the Tco decreases to 150 K at y=0.025y=0.025, it begins to increase with further increase of the doping level. All these phenomena indicate that charge ordering formation is dominated by the spin ordering. As a result, it is experimentally proved that there is strong coupling interaction between charge ordering and spin ordering in the CO/C-type AFM system.

The magnetic properties as well as the electronic transport behaviors of Mn-site electron-doped manganites CaMn1−xWxO3 (0.05≤x≤0.20)(0.05≤x≤0.20) have been studied. For low doping level (x=0.05)(x=0.05), the system shows the coexistence of multi-magnetic phases which is tunable by the applied magnetic field. For x=0.07x=0.07, M–TM–T curve shows an obvious phase transition believed to be from paramagnetism (PM) to G-antiferromagnetism (AFM) at around 190 K. With further increase of tungsten concentration (x=0.10,0.12,0.14)(x=0.10,0.12,0.14), besides a transition at Tl∼Tl∼ 180 K, the system exhibits a peak at ThTh∼∼ 350 K. According to the electron diffraction pattern, it is believed that the peak at ThTh is not a PM to charge ordering (CO) transition but a consequence of orbit ordering. The Jahn–Teller transition induced by the W doping should be responsible for the effect.

In order to experimentally probe the complicated interaction between charge ordering and spin ordering in manganites, two sets of samples Ca0.875Ce0.125Mn1−xCrxO3 and Ca0.875Ce0.125Mn1−yGayO3 (0.0≤x,y≤0.075) have been studied by means of electrical transport measurements, magnetization measurements and electron spin resonance. A large difference between the evolution of the charge ordering temperature Tco in the Cr doping and the Ga doping cases is found. For Cr-doped samples, the Tco decreases to 150 K at x=0.025 and then disappears when x exceeds 0.05. But in Ga-doped samples, although the Tco decreases to 150 K at y=0.025, it begins to increase with further increase of the doping level. All these phenomena indicate that charge ordering formation is dominated by the spin ordering. As a result, it is experimentally proved that there is strong coupling interaction between charge ordering and spin ordering in the CO/C-type AFM system.

The magnetic properties of Y 0.35Ln0.05Ca0.6MnO3 (Ln = La, Pr, Nd, Sm, Gd, Dy) have been investigated thoroughly. The small average cationic radius 〈rA〉 of the present system results in a short-range antiferromagnetic charge-ordering (AFM-CO) state in the manganites. With the decrease of temperature, a super-exchange interaction begins to establish itself between the remaining disordered Mn ions after the formation of the short-range CO state. Then, the reentrant cluster-glass state originates from the frustration between the FM order in the clusters and the AFM interactions present in the background matrix. However, the large magnetic moments of Gd3+ and Dy3+ ions apply an internal magnetic field on the Mn3+ and Mn4+ ions, which results in the suppression of the cluster-glass state.

Polycrystalline samples of Ba-doped Bi0.5Sr0.5MnO3 have been prepared by a standard solid-state reaction. The influence of the Ba doping effect on the structural, macro-magnetic, and micro-magnetic properties of the compounds has been investigated experimentally. All the samples crystallize in an orthorhombic structure and the lattice parameters increase continuously with increasing Ba doping level. Due to the increase of the eg electron bandwidth resulting from the Ba doping, the charge-ordering (CO) transition temperature TCO decreases noticeably. Both the macro-magnetic and the micro-magnetic data show that, in all the samples, only a paramagnetic (PM)/charge-disordered state exists above the CO transition, and only a charge-ordered state coexists with the PM matrix below the CO transition, while an antiferromagnetic (AFM) state coexists with a ferromagnetic (FM) state and a paramagnetic (PM) state at temperatures below the Néel temperature (TN).Highlights► Polycrystalline Ba-doped Bi0.5Sr0.5MnO3 samples have been prepared by a standard solid-state reaction. ► The Ba doping effect on the structural, macro-magnetic, and micro-magnetic properties of the compounds has been investigated. ► Due to the increase of the eg electron bandwidth, TCO decreases noticeably. ► Multiple phases coexist in the compounds.