M?ssbauer analysis of high-energy mechanical-milled sand fraction of a magnetic soil developing on basalt |
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Authors: | Jos?? Fl??vio Marcelino Borges Marlon Luiz Hneda Andr?? Maur??cio Brinatti Jo?o Batista Marimon da Cunha Jadir Aparecido Rosa Jos?? Domingos Fabris |
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Institution: | 1. Department of Physics, State University of Ponta Grossa, Av. Gal. Carlos Cavalcanti 4748, CEP 84030-900, Ponta Grossa, PR, Brazil 2. Institute of Physics, Federal University of Rio Grande do Sul, Av. Bento Gon?alves 9500, CEP 91501-970, Porto Alegre, RS, Brazil 3. Agronomy Institute of Paran??, Polo Regional de Ponta Grossa, BR 376, km 496, CEP 84001-970, Ponta Grossa, PR, Brazil 4. Federal University of Jequitinhonha and Mucuri Valleys (UFVJM), Campus JK, Building 2 office 4, CEP 39100-000, Diamantina, Minas Gerais, Brazil
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Abstract: | A sample of the coarse sand fraction from the soil material of the A-horizon (0?C0.2 m from the soil surface) of a dusky red magnetic Oxisol was submitted to high-energy mechanical milling for different times. This assay aimed mainly at (a) monitoring the individualization of strongly aggregated mineral particles, and (b) measuring the effect of the milling pressure on the mineralogy changes of the material. These data are also intended to experimentally subside any physical model describing the mechanical behavior of the superficial soil layer that is subjected to intensive machine management, in agriculture fields. Powder X-ray data reveal that some mineralogical phases, notably gibbsite, disappear soon after the first few hours milling. The 298 K-transmission Mössbauer spectrum for the non-milled sand sample shows a qualitatively typical pattern for the sand fraction of basalt derived soils, with magnetically ordered sextets, assignable mainly to hematite and maghemite, and an intense central (super)paramagnetic Fe3?+? doublet. For the milled samples, spectra revealed progressive spectral reduction of the magnetic hyperfine structure, with concomitant increase of relative subspectral areas due to (super)paramagnetic phases, as the milling time increased. This result is consistent with the reduction of measured saturation magnetization, from 4.96(8) J T???1 kg???1, for the non-milled sample, to 3.26(7) J T???1 kg???1, for the sample milled for 8 hours. |
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