[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Journal of Physics Condensed Matter: Preface

https://iopscience.iop.org/article/10.1088/1468-6996/16/2/023501/pdf

Recent progress on magnetic iron oxide nanoparticles: synthesis, surface functional strategies and biomedical applications.

Magnetocaloric effect: From materials research to refrigeration devices

A2B′B″O6 perovskites: A review

For advanced lithium-ion battery technology, olivine-based cathodes are considered to be the most dominant and technologically recognized materials. The extraction of lithium ions from olivine LiFePO4 results in the two-phase mixture with heterosite FePO4 exhibiting a deintercalation potential of 3.45 V vs. Li+/Li over a wide range of lithium content. Here, we report the synthesis and characterization of chemically deintercalated heterosite FePO4 with varying crystallite sizes using different analytical techniques. The decrease in the crystallite size of heterosite FePO4 leads to an increase in the lattice parameters including the unit cell volume. The characteristic behavior in the structural properties of heterosite FePO4 shows a strong dependency on the crystallite size which is correlated with the change in the chemical bonding. The volume expansion of the nano-sized heterosite FePO4 with respect to the bulk counterpart is suggested to be a direct consequence of reduced hybridization between the Fe3d and O2p states. Furthermore, the combined X-ray diffraction and Mossbauer spectroscopic studies reveal the appearance of a new phase namely trigonal FePO4 at the lower crystallite sizes due to the enhanced surface energy kinetics. We also find that the observed trigonal FePO4 phase is more magnetically active than the paramagnetic olivine FePO4. For the unique structural advantage of the heterosite phase as an electrode material, the change in bonding characteristics is very useful and can have strong implications on the electronic properties of heterosite FePO4 at the nanoscale level.

Effect of crystallite size on the phase transition behavior of heterosite FePO4.

DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements have been reported for the Co1.1−x
 Zn
 x
 Ge0.1Fe1.2O1 spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important role of magnetic anisotropy (due to the presence of Co2+ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed.

Local canted spin behaviour in Co1.4−x Zn x Ge0.4Fe1.2O4 spinels: A macroscopic, mesoscopic and microscopic study

The nanoparticles of Prussian blue-based molecular magnets, M
 3[Cr(CN)6]2⋅zH2O (where M=Fe, Co, and Ni), prepared by a slow addition (drop by drop) of chemicals using the co-precipitation method, are investigated by means of X-ray diffraction, infra red spectroscopy and dc magnetization measurement techniques The formation of nanoparticles has been confirmed by scanning electron microscopy, whereas the characteristic peak, observed in the range of 1900–2300 cm−1 in the infrared spectra, corresponds to the CN stretching frequency of $\mbox{Cr}^{\mathrm{+III}}$
 –CN–
 $M^{\mathrm{+II}}$
 , and confirms the formation of Prussian blue compounds The results, derived from the Rietveld refinement of X-ray diffraction patterns, reveal that all samples are nanocrystalline in nature with a face-centered cubic crystal structure of space group Fm3m The particle size and the lattice constants decrease with an increasing atomic number of the transition metals (M=Fe, Co and Ni) The magnetization data show a magnetically ordered state of all nanoparticle samples with a low coercivity (except for the Fe3[Cr(CN)6]2⋅zH2O) as well as the remanent magnetization In addition, by varying M with Fe, Co and Ni, the magnetic ordering temperature increases from ∼12 to ∼28 K, whereas the maximum magnetization and the coercive field decrease from ∼14 to ∼45 μB/fu and ∼554 to ∼22 Oe, respectively The observed magnetization behavior has been discussed in terms of the structural changes due to the decreasing particle size as well as the varying nature of the metal ions

Magnetic properties of nanoparticles of Prussian blue-based molecular magnets M3[Cr(CN)6]2 × zH2O (M = Fe, Co, and Ni)

正方格子スピン系(CuBr)Sr 2 Nb 3 O 10 における磁気相関:中性子回折研究

We report, for the first time, temperature dependent pole-reversal of magnetization for La1−xCexCrO3 (x = 0.8, 1.0) nanoparticles. The Rietveld refinement of the x-ray diffraction patterns confirmed the single phase nature of the samples (Orthorhombic: Pbnm). From the transmission electron microscopy (TEM) image, the average particle size is found to be ~ 44 nm. High resolution TEM reveals surface defects/roughness which corroborates a core-shell nature. The magnetic properties of these nanoparticles have been tuned by Ce3+ substitution. The novel pole-reversal phenomenon has been explained using the core-shell model, and can be exploited to fabricate advanced magnetic memory devices.

S. M. Yusuf

Papers

Effect of crystallite size on the phase transition behavior of heterosite FePO4.

Local canted spin behaviour in Co1.4−x Zn x Ge0.4Fe1.2O4 spinels: A macroscopic, mesoscopic and microscopic study

Magnetic properties of nanoparticles of Prussian blue-based molecular magnets M3[Cr(CN)6]2 × zH2O (M = Fe, Co, and Ni)

正方格子スピン系(CuBr)Sr 2 Nb 3 O 10 における磁気相関:中性子回折研究

Pole-reversal of magnetization in core-shell type La1−xCexCrO3(x = 0.8-1.0) nanoparticles