• Current Applied Physics
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• v.18 no.11
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• pp.1190-1195
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• 2018

By employing soft X-ray magnetic circular dichroism (XMCD), soft X-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES), we have investigated the electronic structure of the candidate zero-moment half-metallic $Mn_3Ga$. We have studied the ball-milled and annealed $Mn_3Ga$ powder samples that exhibit nearly zero magnetization. Mn 2p XAS revealed that Mn ions in $Mn_3Ga$ are nearly divalent for both of the Mn ions having the locally octahedral symmetry and those having the locally tetrahedral symmetry. The measured Mn 2p XMCD spectrum of $Mn_3Ga$ is very similar to that of ferrimagnetic $MnFe_2O_4$ having divalent Mn ions. The sum-rule analysis of the Mn 2p XMCD spectrum shows that both the spin and orbital magnetic moments of Mn ions in $Mn_3Ga$ are negligibly small, in agreement with the nearly compensated-ferrimagnetic ground state of $Mn_3Ga$. The valence-band PES spectrum of $Mn_3Ga$ agrees well with the calculated density of states, supporting the half-metallic electronic structure of $Mn_3Ga$.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.130-131
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• 2003

The magnetic and thermal properties of NiFe/IrMn/CoFe with Mn additions have been studied. As grown CoFe pinned-layers with IrMn-Mn have dominantly larger exchange biasing field( $H_{ex}$) and blocking temperature( $T_{b}$) than when pure I $r_{22}$M $n_{78}$ is used. The magnetic properties improve, $H_{ex}$ and $T_{b}$ improve with 77-78 vol% Mn, but drop considerably with more Mn additions, losing magnetic properties of theb NiFe/IrMn/CoFe with addition 0.6 vol % Mn. The average x-ray diffraction peak ratios fcc (111)CoFe of (111)IrM $n_3$ textures for the Mn inserted total vol of 75, 77, and 79 vol% were about 1.4, 0.8, and 0.6, respectively. For the sample without Mn inserted layer, the $H_{ex}$ between I $r_{22}$M $n_{78}$ and CoFe layers is almost nothing. For two multilayer as-grown samples with ultra-thin Mn layers of 77 vol % and 79 vol %, the $H_{ex}$s are 250 Oe and 150 Oe, respectively. In case of IrMn with 77.5 vol% Mn, the $H_{ex}$ was 444 Oe up to 30$0^{\circ}C$ endured of 363 Oe at 40$0^{\circ}C$, respectively. Mn additions improve the magnetic properties and thermal stabilities of NiFe/IrMn/CoFe. Those increase the $H_{ex}$ and $T_{b}$. In applications where higher $H_{ex}$ and $T_{b}$ are accept, proper concentrations of Mn can be used.n can be used.be used.

• Applied Chemistry for Engineering
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• v.33 no.3
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• pp.328-334
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• 2022

For the study of environmental application of natural zeolites (NZ) and red mud (RM), which are discharged from various industrial fields, the catalytic ozonation of 2-butaone (methyl ethyl ketone, MEK) was performed using the Mn-loaded NZ prepared according to the Mn content of 1, 3, 5, 7, and 10 wt%. By the addition of Mn to NZ, the BET (Brunaure-Emmett-Teller) specific surface area of Mn/NZ catalysts decreased while the ratio of Mn³⁺/[Mn³⁺+Mn⁴⁺] intensively increased. Besides, the addition of Mn component to NZ increased the ratio of adsorbed oxygen (O_adsorbed) toward lattice oxygen (O_lattice), O_adsorbed/O_lattice from 0.076 of NZ to 0.465 of 10 wt% Mn/NZ according to the amount of Mn. It is known that the proportion of two species, Mn³⁺ and O_adsorbed, would greatly affect the catalytic activity. However, the balancing between the paired species, Mn³⁺ vs. Mn⁴⁺ and O_adsorbed vs. O_lattice might be more essential for the catalytic ozonation of MEK at room temperature. Among the Mn-loaded NZ catalysts, the 3 wt% Mn/NZ showed the best activity for the removal of MEK and ozone. The 5, 7, and 10 wt% Mn/NZ catalysts are slightly inferior to the 3 wt% Mn/NZ. Compared to the pristine NZ, the Mn/NZ catalysts showed better activity for the catalytic ozonation of MEK. In addition, the 3 wt% Mn/NZ was confirmed to have the most available acid sites among them by the analysis of NH₃-TPD (temperature programmed desorption). This might be the major reason for the best catalytic activity of 3 wt% Mn/NZ together with the adjusted distribution ratios of Mn³⁺/Mn⁴⁺ and O_adsorbed/O_lattice. Considering the result of 3 wt% Mn/NZ, the 3 wt% Mn/RM was prepared to perform the catalytic activity for the removal of MEK and ozone, but the efficiency of 3 wt% Mn/RM was significantly lower than that of the 3 wt% Mn/NZ.

• Korean Journal of Materials Research
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• v.22 no.8
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• pp.385-389
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• 2012

Significant improvements in the switching voltage distribution are required for the development of unipolar resistive memory devices using $MnO_x$ thin films. The $V_{set}$ of the as-grown $MnO_x$ film ranged from 1 to 6.2 V, whereas the $V_{set}$ of the oxygen-annealed film ranged from 2.3 to 3 V. An excess of oxygen in an $MnO_x$ film leads to an increase in $Mn^{4+}$ content at the $MnO_x$ film surface with a subsequent change in the $Mn^{4+}/Mn^{3+}$ ratio at the surface. This was attributed to the change in $Mn^{4+}/Mn^{3+}$ ratios at the $MnO_x$ surface and to grain growth. Oxygen annealing is a possible solution for improving the switching voltage distribution of $MnO_x$ thin films. In addition, crystalline $MnO_x$ can help stabilize the $V_{set}$ and $V_{reset}$ distribution in memory switching in a Ti/$MnO_x$/Pt structure. The improved uniformity was attributed not only to the change of the crystallinity but also to the redox reaction at the interface between Ti and $MnO_x$.

• Analytical Science and Technology
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• v.7 no.4
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• pp.517-526
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• 1994

Large insoluble phases and dispersoids in Al-Li-Cu-Mg-Mn-Zr alloys containing Mn were analyzed with EPMA(Electron Probe Microanalyzer) and SAEM(Scanning Auger Electron Microscope). Morphology, distribution and volume fraction of the large insoluble phase were also analyzed quantitatively by optical microscopy. Mechanical properties were tested at room temperature and at $200^{\circ}C$. With increasing Mn contents, the volume fraction of the large insoluble phases increased steeply, thus decreasing ductility. Mn was found to be very effective for obtaing uniformly distributed fine-grain structures. The alloy containing 0.44 wt% Mn showed the highest tensile strength among Mn-bearing alloys tested.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.7
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• pp.443-447
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• 2014

ZnO crystals with different morphologies were synthesized through a thermal evaporation of Zn-Mn mixtures in air. The morphology was dependant on the Mn content in Zn-Mn mixture. The morphology was changed from rod to tetrapod shape with decreasing Mn content in Zn-Mn mixture. The result indicates that the concentration of Mn might be responsible for the different morphologies of ZnO crystals. XRD spectra showed that the ZnO crystals had a hexagonal wurtzite crystal strutures. For all the samples, room temperature cathodoluminescence spectra showed a ultra-violet emission at 380 nm and a green emission at around 500 nm. However, the intensity ratio of ultra-violet emission to green emission was significantly different with the Mn content in the source material.

• Journal of Powder Materials
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• v.5 no.1
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• pp.35-41
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• 1998

The effect of Mn on the densification and the microstructural change in W heavy alley was investigated with adopting the improved Mn-adding method. In order to avoid the pore formation problems associated with Mn powder mixing to the other constituent powders, Mn was added afterwards to the sintered heavy alloy; Mn powder was spread homogeneously on the surface of the sintered heavy alloy compact, and this Mn powder contained specimen was resintered at the same sintering temperature. As expected, the resintered specimen showed the pore free microstructure because Mn was reduced separately from the other constituent elements. It was also founded that W grains grew rapidly at the initial stage of resintering treatment due to the activated reprecipitation of the excess W atoms substituted by Mn atoms, but the growth rate of W grains was slowly lowered with the prolonged sintering time, especially, compared to the Mn free heavy alloy. Such a retardation of grain growth should be attributed to the decreased W solubility in the Mn contented matrix phase. Furthermore, Mn addition resulted in the decrease of contiguity by improving the wetting between matrix phase and W grain.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.6
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• pp.246-252
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• 2011

The semiconducting $MnSi_{1.73}$ compound has been recognized as a thermoelectric material with excellent oxidation resistance and stable characteristics at elevated temperature. In the present work, we applied mechanical alloying (MA) technique to produce $MnSi_{1.73}$ compound using a mixture of elemental manganese and silicon powders. The mechanical alloying was carried out using a Fritsch P-5 planetary mill under Ar gas atmosphere. The MA powders were characterized by the X-ray diffraction with Cu-$K{\alpha}$ radiation, thermal analysis and scanning electron microscopy. Due to the observed larger loss of Si relative to Mn during mechanical alloying of $MnSi_{1.73}$, the starting composition of a mixture Mn-Si was modified to $MnSi_{1.83}$ and then $MnSi_{1.88}$. The single $MnSi_{1.73}$ phase has been obtained by mechanical alloying of $MnSi_{1.88}$ mixture powders for 200 hours. It is also found that the grain size of $MnSi_{1.73}$ compound powders analyzed by Hall plot method is reduced to 40 nm after 200 hours of milling.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.1
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• pp.36-41
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• 2000

We studied the exchange anisotropy of Ni-Fe/Co-Fe/Mn-Ir/Cu/buffer/Si multilayers using D.C magnetron sputtering technique. Generally, Ni-Fe/Mn-Ir/buffer(Cu)/Si multilayers cannot pin the ferromagnetic layer for the lower exchange biased field. We got $H_{ex}$ ex/ increased by two times, after using Cu/Ta as buffer layer to get larger grain size of Mn-Ir layer and inserting very thin Co-Fe layer between the Ni-Fe layer and the Mn-Ir layer to get improved grain-to-grain epitaxy relation at the interface between Ni-Fe layer and Mn-Ir layer. The variation of $H_{ex}$ by thickness of Mn-Ir layer in ferromagnete/Mn-Ir/buffer/Si multilayers is different to that in Mn-Ir/ferromagnete/buffer/Si multilayers, because the volume distribution of grain size of Mn-Ir layer and the exchange energy at the interface between the Mn-Ir and the ferromagnetic layers is different for stacking sequence.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.213-218
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• 2004

Be-codoped GaMnAs layers were systematically grown via molecular beam epitaxy with varying Mn- and Be-flux. Mn flux was controlled to cover from solid solution type GaMnAs to precipitated GaMnAs. Two Be flux were chosen to exhibit semiconducting and metallic resistivity in the grown layers. The structural, electrical, and magnetic properties of GaAs:(Mn, Be) were investigated. The lightly Be-codoped GaMnAs layers showed ferromagnetism at room temperature, but did not reveal magnetotransport due to small magneto-resistance and high resistance of the matrix. However, room temperature magnetotransport could be observed in the degenerate Be-codoped GaMnAs layers, and which was assisted by the high conductivity of the matrix. The Be-codoping has promoted segregation of new ferromagnetic phase of MnGa as well as MnAs.