Magnetocrystalline anisotropy of cementite pseudo single crystal fabricated under a rotating magnetic field

Yamamoto, Sumio; Terai, Tomoyuki; Fukuda, Takashi; Satō, Kazunori; Kakeshita, Tomoyuki; Horii, Shigeru; Ito, Mikio; Yonemura, Masao

doi:10.1016/j.jmmm.2017.10.114

Cited by 19 publications

(15 citation statements)

References 5 publications

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“…The T C temperature reported for bulk cementite is about 483 K [ 78 , 79 ], and the characteristic temperature at which magnetic ordering disappeared in our Fe 3 C-NPs was about 430 K. Therefore, in our calculations of l ex and l K (defined below) for bulk Fe 3 C, we used A(T) = 6.8 × 10 −11 J/m at 295 K. The estimated l lex values were about 9.8 nm ( d c ≈ 51 ÷ 71 nm) and 10.1 nm ( d c ≈ 52 ÷ 73 nm) at the low and high temperature, respectively. Using reported values of the magnetocrystalline anisotropy energy ( K ) of about 334 kJ/m 3 and 150 kJ/m 3 at 5 K and 300 K, respectively, for bulk Fe 3 C [ 80 ], we obtained the crystalline anisotropy length

to be about 17 nm ( d c ≈ 88 ÷ 122 nm) at the low temperature and about 21 nm ( d c ≈ 109 ÷ 151 nm) at room temperature. The characteristic d t diameter can be estimated under conditions where the energy of magnetization reversal is equal to the thermal energy [ 69 ].…”

Section: Discussionmentioning

confidence: 99%

Effect of Grinding and the Mill Type on Magnetic Properties of Carboxylated Multiwall Carbon Nanotubes

et al. 2021

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The influence of the grinding process on the magnetic properties of as prepared and functionalized multiwall carbon nanotubes (MWCNTs) is presented. We have observed that 3 h mechanical grinding at 400 rpm in contrast to functionalization does not remove the iron contamination from MWCNTs. However, it changes the Fe chemical states. The magnetic properties of iron nanoparticles (Fe-NPs) embedded in the carbon matrix of MWCNTs have been analyzed in detail. We have proven that single-domain non-interacting Fe(C,O)-NPs enriched in the Fe3C phase (~10 nm) enclosed inside these nanotubes are responsible for their magnetic properties. Mechanical grinding revealed a unique impact of -COOH groups (compared to -COONH4 groups) on the magnetism of functionalized MWCNTs. In MWCNT-COOH ground in a steel mill, the contribution of the Fe2O3 and α-Fe phases increased while the content of the magnetically harder Fe3C phase decreased. This resulted in a 2-fold coercivity (Hc) decrease and saturation magnetization (MS) increase. A 2-fold remanence (Mr) decrease in MWCNT-COOH ground in an agate mill is related to the modified Fe(C,O)-NP magnetization dynamics. Comparison of the magnetostatic exchange and effective anisotropy length estimated for Fe(C,O)-NPs allows concluding that the anisotropy energy barrier is higher than the magnetostatic energy barrier. The enhanced contribution of surface anisotropy to the effective anisotropy constant and the unique effect of the -COOH groups on the magnetic properties of MWCNTs are discussed. The procedure for grinding carboxylated MWCNTs with embedded iron nanoparticles using a steel mill has a potential application for producing Fe-C nanocomposites with desired magnetic properties.

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Section: Discussionmentioning

confidence: 99%

Effect of Grinding and the Mill Type on Magnetic Properties of Carboxylated Multiwall Carbon Nanotubes

et al. 2021

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“…However, the trend in measured coercivities perfectly follows the ones in literature. While the magneto-crystalline anisotropy only drops by a bit more than 10% for bcc-Fe [ 23 , 24 , 25 ], the drop for Fe 3 C would be much larger, about 50% [ 38 ]. Taking these results and the values of the volume saturation magnetization, the deformed wires behave magnetically like bcc Fe.…”

Section: Resultsmentioning

confidence: 99%

Soft Magnetic Properties of Ultra-Strong and Nanocrystalline Pearlitic Wires

et al. 2021

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The paper describes the capability of magnetic softening of a coarse-grained bulk material by a severe deformation technique. Connecting the microstructure with magnetic properties, the coercive field decreases dramatically for grains smaller than the magnetic exchange length. This makes the investigation of soft magnetic properties of severely drawn pearlitic wires very interesting. With the help of the starting two-phase microstructure, it is possible to substantially refine the material, which allows the investigation of magnetic properties for nanocrystalline bulk material. Compared to the coarse-grained initial, pearlitic state, the coercivities of the highly deformed wires decrease while the saturation magnetization values increase—even beyond the value expectable from the individual constituents. The lowest coercivity in the drawn state is found to be 520 A m−1 for a wire of 24-µm thickness and an annealing treatment has a further positive effect on it. The decreasing coercivity is discussed in the framework of two opposing models: grain refinement on the one hand and dissolution of cementite on the other hand. Auxiliary measurements give a clear indication for the latter model, delivering a sufficient description of the observed evolution of magnetic properties.

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“…For the triclinic system, there is no general relationship between the crystallographic and magnetic axes. Owing to their biaxial magnetic nature, biaxial crystals can be aligned biaxially (or three-dimensionally) if an appropriate dynamic magnetic field (DMF) is applied [21][22][23][24][25]. Among the biaxial crystals, most orthorhombic crystals exhibit only one orientation under DMF, because the crystallographic and magnetic susceptibility axes coincide.…”

Section: Resultsmentioning

confidence: 99%

X-ray Single-Crystal Structural Analysis of a Magnetically Oriented Monoclinic Microcrystal Suspension of α-Glycine

et al. 2019

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We previously reported on a method for X-ray single-crystal structure determination from a powder sample via a magnetically oriented microcrystal suspension (MOMS). The method was successfully applied to orthorhombic microcrystals (L-alanine, P212121). In this study, we apply this method to monoclinic microcrystals. Unlike most of the orthorhombic MOMSs, monoclinic MOMSs exhibit two or four orientations with the same magnetic energy (we refer to this as twin orientations), making data processing difficult. In this paper, we perform a MOMS experiment for a powder sample of monoclinic microcrystal (α-glycine, P21/n) to show that our method can also be applied to monoclinic crystals. The single-crystal structure determined in this work is in good agreement with the reported one performed on a real single crystal. Furthermore, the relationship between the crystallographic and magnetic susceptibility axes is determined.

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Magnetocrystalline anisotropy of cementite pseudo single crystal fabricated under a rotating magnetic field

Cited by 19 publications

References 5 publications

Effect of Grinding and the Mill Type on Magnetic Properties of Carboxylated Multiwall Carbon Nanotubes

Effect of Grinding and the Mill Type on Magnetic Properties of Carboxylated Multiwall Carbon Nanotubes

Soft Magnetic Properties of Ultra-Strong and Nanocrystalline Pearlitic Wires

X-ray Single-Crystal Structural Analysis of a Magnetically Oriented Monoclinic Microcrystal Suspension of α-Glycine

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