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Gamma-ray production cross section excitation functions have been measured for $30$, $42$, $54$ and $66$ MeV proton beams accelerated onto targets of astrophysical interest, $^{nat}$C, C + O (Mylar), $^{nat}$Mg, $^{nat}$Si and $^{56}$Fe, at the Sector Separated Cyclotron (SSC) of iThemba LABS (near Cape Town, South Africa). The AFRODITE array equipped with 8 Compton suppressed HPGe clover detectors was used to record $\gamma$-ray data. For known, intense $\gamma$-ray lines the previously reported experimental data measured up to $E_{p}\simeq$ $25$ MeV at the Washington and Orsay tandem accelerators were extended to higher proton energies. Our experimental data for the last 3 targets are reported here and discussed with respect to previous data and the Murphy \textit{et al.} compilation [ApJS 183, 142 (2009)], as well as to predictions of the nuclear reaction code TALYS. The overall agreement between theory and experiment obtained in first-approach calculations using default input parameters of TALYS has been appreciably improved by using modified optical model potential (OMP), deformation, and level density parameters. The OMP parameters have been extracted from theoretical fits to available experimental elastic/inelastic nucleon scattering angular distribution data by means of the coupled-channels reaction code OPTMAN. Experimental data for several new $\gamma$-ray lines are also reported and discussed. The astrophysical implications of our results are emphasised., Comment: 22 pages, 10 figures, five tables; regular article submitted to Phys Rev C

Gamma-ray production cross section excitation functions have been measured for $30$, $42$, $54$ and $66$ MeV proton beams accelerated onto targets of astrophysical interest, $^{nat}$C, C + O (Mylar), $^{nat}$Mg, $^{nat}$Si and $^{56}$Fe, at the Sector Separated Cyclotron (SSC) of iThemba LABS (near Cape Town, South Africa). The AFRODITE array equipped with 8 Compton suppressed HPGe clover detectors was used to record $\gamma$-ray data. For known, intense $\gamma$-ray lines the previously reported experimental data measured up to $E_{p}\simeq$ $25$ MeV at the Washington and Orsay tandem accelerators were extended to higher proton energies. Our experimental data for the last 3 targets are reported here and discussed with respect to previous data and the Murphy \textit{et al.} compilation [ApJS 183, 142 (2009)], as well as to predictions of the nuclear reaction code TALYS. The overall agreement between theory and experiment obtained in first-approach calculations using default input parameters of TALYS has been appreciably improved by using modified optical model potential (OMP), deformation, and level density parameters. The OMP parameters have been extracted from theoretical fits to available experimental elastic/inelastic nucleon scattering angular distribution data by means of the coupled-channels reaction code OPTMAN. Experimental data for several new $\gamma$-ray lines are also reported and discussed. The astrophysical implications of our results are emphasised., Comment: 22 pages, 10 figures, five tables; regular article submitted to Phys Rev C

Manganites-based perovskites, having the general formula LnAMnMO where Ln is a rare earth element (Ln = Pr , La ,..) and A is an alkaline earth element (A = Sr , Ba , Ca ,..), were the center of interest of many studies because of their outstanding physicochemical properties and because they can play an important role in various applications. The aim of this work is the development with mechanical alloying method and study of physicochemical properties of new manganites. This work focuses on the development and characterization of series LaCaSrMnFeO (0 ≤ x≤ 0. 3. The structural study showed that the cell parameters of the samples increase with the increase in the rate of iron and causing the expansion of the orthorhombic distortion. This result is confirmed by the tolerance factor tg (0. 75 < tg< 0. 95 : orthorhombic structure). The magnetic study showed that the substitution of Mn by Fe in these series indicates a ferromagnetic-paramagnetic transition. This transition accompanied with a decrease in the Curie temperature (T).

New complex perovskites of the series CaCu(MnRe)O have been prepared from citrate precursors under moderate pressure conditions of 2 GPa and 1000 °C, in the presence of KClO as oxidizing agent to stabilize Mn/Mn mixed valence. The polycrystalline samples have been characterized by x-ray diffraction, neutron powder diffraction (NPD), magnetic, and magnetotransport measurements. The crystal structures are cubic, space group Im-3. The unit-cell parameters increase from a = 7.2379(2) Å for the parent (x = 0) compound to a = 7.2420(4) Å for CaCu(MnRe)O. Both oxides adopt a superstructure of the perovskites ABO with long-range 1:3 ordering for Ca and Cu ions at the A sublattice. For the compound doped with Re (x = 0.1), the result of a NPD study shows that Re ions are randomly located at the octahedral positions, being the (Mn,Re)O octahedra strongly tilted, with superexchange (Mn,Re)-O-(Mn,Re) angles of 142.03°. Neutron diffraction data clearly show that some Mn ions are located together with Cu at the square-planar 6b positions. The magnetic structure determined from low-temperature NPD data unveils a ferromagnetic coupling between (Mn,Re) spins at octahedral positions and weak antiferromagnetism with (Cu,Mn) spins. Interestingly, an enhancement of the magnetoresistance effect is observed for the Re-doped compound, well beyond that found for the parent perovskite.

New compounds of the series CaCu3(Mn4−xAlx)O12 have been prepared under high pressure conditions (2 GPa), in the presence of KClO4 as oxidizing agent to stabilize Mn3+,4+ mixed valence. The polycrystalline samples have been characterized by x-ray diffraction, neutron powder diffraction (NPD), magnetic, and magnetotransport measurements. All the samples are cubic, space group Im-3. These oxides adopt a superstructure of ABO3 perovskite given by the long-range 1:3 ordering of Ca2+ and Cu2+ ions at the A sublattice. The NPD study for x = 0.4 shows that Al3+ ions are statistically distributed at the octahedral positions, being the (Mn,Al)O6 octahedra strongly tilted, with superexchange (Mn,Al)-O-(Mn,Al) angles of 142.1°. Also, neutron data clearly show that some Mn3+ ions (0.65(2) per formula) are located together with Cu2+ at the square-planar 6b positions. Regarding the magnetic properties, all the compounds present a spontaneous increase of the magnetization below TC, typical of ferro-or ferrimagnetic materials, with TC decreasing upon Al introduction. The magnetic structure determined from low-temperature NPD data unveils a ferromagnetic coupling between (Cu2+, Mn3+)6b spins and Mn8c spins at octahedral positions; this is in contrast with the ferrimagnetic structure observed for RCu3Mn4O12 and CaCu3Mn4O12, where an AFM coupling is observed between both magnetic sublattices. Interestingly, an enhancement of the magnetoresistance effect is observed for x = 0.2, well beyond that found for the parent compound. This effect, in materials subtly doped with non-magnetic elements at the Mn positions, may be of interest for applications.