ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Mn and Cr powders were produced from electrolytic Mn and Cr by ball milling in a stainless steel container with carbon steel balls. The milling time, t, varied from 5 min to 8 h. Structures were investigated by x-ray and electron microscopy. Chemical compositions of samples were checked by flame atomic absorption spectrometry. The magnetization was measured by induction method in a pulsed magnetic field up to 10 T. The main part of Mn and Cr powder volume was occupied by α-Mn and b.c.c. Cr, respectively. Diffraction peaks became vaster and more asymmetric with increasing t due to the onset of defects of the structure. The presence of MnO was observed in the Mn sample after 8 h of milling. The size of Mn and Cr particles over same critical t (for chromium t=100 min) was no more than 1 mm. A noticeable Fe content, which increases at higher t, was observed. The Mössbauer spectra of Cr and Mn samples showed the lines of α-Fe and γ-Fe. High values of saturation magnetization, σ, up to 5.4 emu/g, and susceptibility and existence of the hysteresis in low fields at temperatures up to 360 K, indicate ferromagnetic ordering of the samples. Within the range of 78–360 K σ only slightly depends on temperature, but noticeably grows with increasing t at fixed temperature in Cr powders, remaining practically constant in Mn powders. No correlation could be observed between Fe content and σ : the latter remained the same in Mn with Fe concentration increasing, but in Cr, as Fe concentration increased sevenfold, it grew by four times. Spontaneous magnetization per mass unit of Fe, σ, was sufficiently lower than that of pure α-Fe (220 emu/g). The obtained values of σ correspond neither to Fe solid solution nor to pure Cr or Mn. Elucidation of the obtained results can be done both by the presence of α-Fe particles and by variation of exchange interactions caused by sample defects. A noticeable difference of σ values from those properties of bulk α-Fe can be explained by γ-Fe availability and grinding of particles being smaller than single domain sizes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.352616
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