• Journal of Magnetics
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• 제16권2호
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• pp.134-139
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• 2011

Magnetic properties of highly zinc-substituted manganese ferrites are discussed on the basis of cation distribution. High throughput neutron powder diffractometry indicates that the prepared samples possess a nearly normal spinel structure, where the substitution of nonmagnetic zinc ions mainly causes the dilution of magnetic ions in the A-sublattice and consequently affects bond-randomness in the B-sublattice. On the other hand, the estimated occupancy of manganese ions in the B site indicates that random anisotropy effects due to local Jahn-Teller distortions gradually weaken with the substitution. Bulk magnetometry indicates that the substitution smears the transition from a paramagnetic phase to a soft-magnetic phase. Furthermore, at lower temperatures, such a soft-magnetic phase is destabilized and a magnetic glassy state appears. These features of the magnetic properties of dilute spinel ferrites are discussed from the viewpoint of the above-mentioned various types of disorders.

• Bulletin of the Korean Chemical Society
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• 제34권7호
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• pp.2195-2198
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• 2013

• 대한금속재료학회지
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• 제50권3호
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• pp.248-255
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• 2012

AlN thin films containing various amounts of Co, AlN-Co, and Al-Co alloy particles were prepared using a two-facing-target type dc reactive sputtering (TFTS) system. The as-deposited films exhibited the variable nature expected from an AlN-rich phase, and an amorphous-like phase, depending on the Co content in the films. Specific favorable microstructures were prepared by optimizing annealing conditions. Those microstructures and their magnetic properties and resistivity were investigated. As-deposited films showed very small saturation magnetization and an amorphous-like structure. However, when annealed, the as-deposited amorphous-like phase decomposes into phases of AlN, Co and Al-Co. These annealing induced changes in the microstructure improve the magnetization and resistivity of the films. Further improvement of soft magnetic properties could lead to the material being used for high density magnetic recording head material.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.120-121
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• 2006

Magnetic properties of nanostructured materials are affected by the microstructures such as grain size (or particle size), internal strain and crystal structure. Thus, it is necessary to study the synthesis of nanostructured materials to make significant improvements in their magnetic properties. In this study, nanostructured Fe-20at.%Co and Fe-50at.%Co alloy powders were prepared by hydrogen reduction from the two oxide powder mixtures, $Fe_2O_3$ and $Co_3O_4$. Furthermore, the effect of microstructure on the magnetic properties of hydrogen reduced Fe-Co alloy powders was examined using XRD, SEM, TEM, and VSM.

• 한국전기전자재료학회논문지
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• 제14권1호
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• pp.74-83
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• 2001

In this study, the optimum structure of a magnetic thin film inductor was designed for application of DC-DC converters. The Ni$\sub$81/Fe$\sub$19/ (at%) alloy was selected as a high-frequency($\geq$MHz) magnetic thin film magnetron sputtering system. As-deposited NiFe thin films show similar magnetic properties compared to bulk NiFe alloys, indicating that they have a good film quality. The optimum design of dolenoid-type magnetic thin film inductors was performed utilizing a Maxwell computer simulator (Ansoftt HFSS V7.0 for PC) and parameters obtained from the magnetic properties of magnetic core materials selected. The high-frequency characteristics of the inductance(L) and quality factor(Q) obtained for the designed inductors through simulation agreed well with those obtained by theoretical calculations, confirming that the simulated result is realistic. The optimum structure of high-performance (Q$\geq$60, L = 1${\mu}$H, efficiency $\geq$90%), high-frequency ($\geq$5MHz), and solenoid-type magnetic thin film inductors was designed successfully.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4251-4254
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• 2012

• 한국재료학회지
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• 제16권9호
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• pp.578-583
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• 2006

We studied the physical properties of Ni-Zn ferrites by adding different chemicals such as $SO_4$, Cl, and $NO_3$. Specimens were prepared by the coprecipitation method and sintered at temperatures $950^{\circ}C,\;1,150^{\circ}C,\;and\;1,350^{\circ}C$, respectively. X-ray diffractions showed a spinel structure and the optical microscopy revealed grain size of 0.3 to 0.6 ${\mu}m$. The optimum sintering temperature to obtain fine, sintered microstructure depended on the additive : Cl and $NO_3\;at\;950^{\circ}C\;and\;SO_4\;at\;1,150^{\circ}C$. According to particle size analysis, higher magnetic permeability and magnetization value were observed with Cl and $NO_3\;than\;SO_4$. As sintering temperature was raised from $950^{\circ}C$ to $1,350^{\circ}C$, the average grain diameter, initial permeability and the magnetic moment also increased.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.369-376
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• 2000

Change of magnetic properties in CoCrPt/Ti perpendicular media with varying CoCrPt films thickness has been studied. As CoCrPt films thickness increase, the Ms(magnetization saturation) drastically increases at thinner thickness and gradually increases with further increase in thickness from 25nm. This Ms behaviour is associated with primarily the formation of "amorphous-like" reacted layer by intermixing of CoCrPt and Ti at CoCrPt/Ti interface and secondarily change of Cr segregation mode with varying the CoCrPt films thickness. Magnetic domain structure distinctively changes with increasing CoCrPt magnetic layer(ML) thickness. Also the strength of exchange coupling measured from the slope in demagnetizing region in M-H loop changes with ML thickness. Details of the above magnetic properties will be discussed. The expansion of lattice parameters a and c at thinner thickness suggests that Cr segregation mode may be connected with the residual stress of the films. Finally, negative nucleation field(Hn) behaviour with the exchange slope will be reported.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4231-4234
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• 2012

• Journal of Magnetics
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• 제19권2호
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• pp.101-105
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• 2014

In this work, Zinc ferrite nanoparticles have been prepared by various methods, conventional (ZC), mechanochemical processing (ZM) and Sol-Gel (ZS) method, to compare their structural and magnetic properties. The cation distribution obtained from XRD shows the degrees of inversions are 4%, 14.8%, and 16.4% from the normal $ZnFe_2O_4$ structure. Fourier transform infrared spectroscopy (FT-IR) confirms changes in cation distribution of $ZnFe_2O_4$ fabricated by sol-gel and mechanochemical processing. The $^{57}Fe$ M$\ddot{o}$ssbauer spectra of the samples were recorded at room temperature. The spectra exhibit a line broadening. The magnetic properties of the samples were studied by vibration sample magnetometer (VSM) at room temperature and the results show that the sample ZM has ferrimagnetic behaviour.