Search results for: K. Hono

Items from 1 to 20 out of 310 results

article

Time domain magnetization dynamics study to estimate interlayer exchange coupling constant in Nd-Fe-B/Ni80Fe20 films

R. Mandal, D. Ogawa, Y. Tamazawa, K. Ishioka, more

Journal of Magnetism and Magnetic Materials > 2018 > 468 > C > 273-278

Interlayer exchange coupling (J_ex) between a hard magnetic Nd-Fe-B layer and a soft magnetic Ni₈₀Fe₂₀ layer is studied by means of time-resolved magneto-optical Kerr effect (TRMOKE) microscope. Whereas a single 16 nm thick Nd-Fe-B layer without Ni₈₀Fe₂₀ showed high coercivity of μ₀H_c = 2 T and resonance frequency of f_r = 161 GHz at external bias magnetic field of μ₀H_b = 2 T due to the high anisotropy...

article

Bake-hardenable Mg–Al–Zn–Mn–Ca sheet alloy processed by twin-roll casting

M.Z. Bian, T.T. Sasaki, T. Nakata, Y. Yoshida, more

Acta Materialia > 2018 > 158 > C > 278-288

Mg–1.3Al–0.8Zn–0.7Mn–0.5Ca (wt.%) (AZMX1110) alloy sheet produced by low-cost twin-roll casting process exhibits excellent room temperature formability with a large Index Erichsen (I.E.) value of 7.8 mm at room temperature in a solution treated condition (T4). The large I.E. value is associated with a weak basal texture in the T4-condition. This alloy shows rapid age-hardening response at 170 °C,...

article

Microstructure of a Dy-free Nd-Fe-B sintered magnet with 2 T coercivity

X.D. Xu, T.T. Sasaki, J.N. Li, Z.J. Dong, more

Acta Materialia > 2018 > 156 > C > 146-157

We investigated the microstructure of the Dy-free high coercivity sintered magnet that was developed by optimizing the chemical composition of Nd-Fe-B sintered magnet with 0.1 at.%Ga doping in order to understand the reasons for the high coercivity of μ₀H_c = 2.0 T and the improved squareness of 0.95 compared to a recently developed 0.5 at. %Ga doped magnet. The as-sintered 0.1Ga sample shows a relatively...

article

Reprint of Prospect for HRE-free high coercivity Nd-Fe-B permanent magnets

K. Hono, H. Sepehri-Amin

Scripta Materialia > 2018 > 154 > C > 277-283

Recent state-of-the-art microstructure investigations on Nd-Fe-B sintered magnets have revealed that the Nd₂Fe₁₄B grains in conventional sintered magnets are exchange-coupled through ferromagnetic grain boundary phase and the coercivity is governed by domain wall pinning, while exchange-decoupled sintered magnets can be processed by tuning the chemical composition to a slightly Nd-rich and B-lean...

article

Searching the weakest link: Demagnetizing fields and magnetization reversal in permanent magnets

J. Fischbacher, A. Kovacs, L. Exl, J. Kühnel, more

Scripta Materialia > 2018 > 154 > C > 253-258

Magnetization reversal in permanent magnets occurs by the nucleation and expansion of reversed domains. Micromagnetic theory offers the possibility to localize the spots within the complex structure of the magnet where magnetization reversal starts. We compute maps of the local nucleation field in a Nd₂Fe₁₄B permanent magnet using a model order reduction approach. Considering thermal fluctuations...

article

Effects of rolling conditions on the microstructure and mechanical properties in a Mg–Al–Ca–Mn–Zn alloy sheet

M.Z. Bian, T.T. Sasaki, T. Nakata, S. Kamado, more

Materials Science and Engineering: A > 2018 > 730 > C > 147-154

Mg–1.2Al–0.3Ca–0.4Mn–0.3Zn (AXMZ1000) (wt%) alloy was rolled in three different conditions in order to understand the effects of the rolling conditions on the microstructure and mechanical properties. The sheet subjected to high temperature reheating at 500 °C for 5 min prior to each 100 °C rolling delivers the highest Index Erichsen (I.E.) value of 7.0 mm. The sheet rolled at 300 °C with 500 °C reheating...

article

Coercivity enhancement of hot-deformed Ce-Fe-B magnets by grain boundary infiltration of Nd-Cu eutectic alloy

Xin Tang, H. Sepehri-Amin, T. Ohkubo, M. Yano, more

Acta Materialia > 2018 > 144 > C > 884-895

The coercivity of hot-deformed Ce-Fe-B magnet was substantially improved from ∼8 × 10⁻⁴ to ∼0.7 T by the grain boundary infiltration of Nd-Cu eutectic alloy. Transmission electron microscopy have shown the formation of (Nd_xCe_1-x)₂Fe₁₄B shell in Ce₂Fe₁₄B grains and the increase of rare earth elements in the intergranular phases after the process. The former enhances the anisotropy field of the shell...

article

Improving mechanical properties and yield asymmetry in high-speed extrudable Mg-1.1Al-0.24Ca (wt%) alloy by high Mn addition

T. Nakata, C. Xu, R. Ajima, Y. Matsumoto, more

Materials Science and Engineering: A > 2018 > 712 > C > 12-19

The chemical composition of a Mg-1.1Al-0.33Ca-0.44Mn (wt%) alloy, AXM10304, has been optimized for high speed extrusion. The extrudability is substantially improved from 24m/min to 60m/min by slightly reducing the Ca content from 0.33wt% to 0.24wt%. Then, the effect of Mn content on the mechanical properties and microstructures of extruded Mg-1.1Al-0.24Ca based alloys were investigated. In a solution-treated...

article

Enhancement of current-perpendicular-to-plane giant magnetoresistive outputs by improving B2-order in polycrystalline Co2(Mn0.6Fe0.4)Ge Heusler alloy films with the insertion of amorphous CoFeBTa underlayer

S. Li, T. Nakatani, K. Masuda, Y. Sakuraba, more

Acta Materialia > 2018 > 142 > C > 49-57

We studied the origin of the enhancement of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) effect by inserting a thin amorphous CoFeBTa (CFBT) underlayer below a Co₂(Mn_0.6Fe_0.4)Ge (CMFG) Heusler alloy ferromagnetic (FM) layer. Large magnetoresistance ratio of ∼25% and resistance change-area product of ∼7.5 mΩ μm² were obtained at room temperature by inserting a CFBT (1.2 nm) underlayer...

article

Micromagnetic Studies at Finite Temperature on FePt–C Granular Films

Junjie Song, J. Wang, Dan Wei, Y. K. Takahashi, more

IEEE Transactions on Magnetics > 2017 > 53 > 11 > 1 - 4

A new micromagnetic method using the hybrid Monte Carlo (HMC) algorithm has been developed, and the magnetic properties at finite temperature can be simulated. In this paper, the HMC micromagnetics are applied on the polycrystalline FePt–C granular films for heat-assisted magnetic recording, where the significant parameters such as the temperature-dependent saturation magnetization

$M_{s}$

(T) are...

article

Intrinsic hard magnetic properties of Sm(Fe1−xCox)12 compound with the ThMn12 structure

Y. Hirayama, Y.K. Takahashi, S. Hirosawa, K. Hono

Scripta Materialia > 2017 > 138 > C > 62-65

We have grown Sm(Fe_1−xCo_x)₁₂ (x=0, 0.1 and 0.2) films epitaxially on V(001) buffered MgO(001) single crystalline substrates in order to investigate the intrinsic hard magnetic properties of the Co substituted SmFe₁₂ phase with the ThMn₁₂ structure. We found Sm(Fe_0.8Co_0.2)₁₂ has excellent intrinsic hard magnetic properties with spontaneous magnetization of 1.78T, anisotropy field of 12T and Curie temperature...

article

A heat-treatable Mg–Al–Ca–Mn–Zn sheet alloy with good room temperature formability

M.Z. Bian, T.T. Sasaki, B.C. Suh, T. Nakata, more

Scripta Materialia > 2017 > 138 > C > 151-155

A newly developed magnesium sheet alloy, Mg–1.1Al–0.3Ca–0.2Mn–0.3Zn (at.%), shows a large Index Erichsen value of 7.7mm in a solution treated (T4) condition due to a weak basal texture developed by the trace addition of Zn. Subsequent artificial aging at 200°C for 1h (T6) significantly increases the 0.2% proof strength from 144MPa to 204MPa. This improvement in strength by the T6 treatment is associated...

article

Magnetization reversal of exchange-coupled and exchange-decoupled Nd-Fe-B magnets observed by magneto-optical Kerr effect microscopy

M. Soderžnik, H. Sepehri-Amin, T.T. Sasaki, T. Ohkubo, more

Acta Materialia > 2017 > 135 > C > 68-76

We observed the magnetization reversals of exchange-coupled and exchange-decoupled Nd-Fe-B sintered magnets with coercivities of 1.16 and 1.80 T, respectively, by magneto-optical Kerr effect (MOKE) microscopy. The cascade propagation of reversed magnetic domain throughout multiple grains was observed in the standard sintered magnet, in which Nd₂Fe₁₄B grains are believed to be exchange-coupled through...

article

Pt surface segregation in L10-FePt nano-grains

H. Sepehri-Amin, H. Iwama, G. Hrkac, K.T. Butler, more

Scripta Materialia > 2017 > 135 > C > 88-91

The influence of the chemical compositions of FePt films on the surface segregations of Pt was investigated by cross-sectional high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) of L1₀-FePt granular films grown on single crystalline MgO substrates. Ab initio atomistic simulations revealed the surface segregation of Pt is detremental for the magentocrystalline anisotropy...

article

Improved (001)-texture of FePt-C for heat-assisted magnetic recording media by insertion of Cr buffer layer

T. Shiroyama, J. Wang, A. Felicia, Y.K. Takahashi, more

Journal of Magnetism and Magnetic Materials > 2017 > 432 > C > 129-134

FePt-C granular films deposited on MgO underlayers are the prototype media for heat-assisted magnetic recording. To reduce the in-plane magnetic component in the FePt-C media, we investigated the effect of Cr buffer layers on the crystallographic textures of the MgO underlayers and the resultant magnetic properties of the FePt-C layers. By growing a MgO underlayer on a Cr buffer layer, the (001) texture...

article

Strong and ductile age-hardening Mg-Al-Ca-Mn alloy that can be extruded as fast as aluminum alloys

T. Nakata, C. Xu, R. Ajima, K. Shimizu, more

Acta Materialia > 2017 > 130 > C > 261-270

We have developed a wrought magnesium alloy, Mg-1.3Al-0.3Ca-0.4Mn (wt.%) or AXM10304, that can be extruded at a very high die-exist speed of 24 m/min, comparable to the extrusion speed for aluminum alloys, and that exhibits an excellent combination of strength and elongation after an age-hardening, i.e., a tensile 0.2% proof stress of 287 MPa and an elongation of 20%. The high tensile proof stress...

chapter

Enhanced CPP-GMR effect by improved B2-order of Co₂(Mn_0.6Fe_0.4)Ge Heusler layer deposited on amorphous CoFeBTa underlayer: A quantitative estimation of site-disordering by anomalous x-ray diffraction

S. Li, T. Nakatani, Y. Sakuraba, H. Tajiri, more

2017 IEEE International Magnetics Conference (INTERMAG) > 1

2017 IEEE International Magnetics Conference (INTERMAG)

Due to the theoretically predicted half-metallicity together with high Curie temperature well beyond room temperature, Co₂YZ type (Y = Mn, Fe, and Z = Si, Ge, Al, Ga etc.) full Heusler alloys have received extensive research interests for spintronic device applications such as read head sensors of hard disk drive using current-perpendicular-to-plane giant magnetoresistance (CPP-GMR).

chapter

Origin of in-plane component for L1₀-FePt granular films deposited on MgO single crystal substrate

J. Wang, Y. Takahashi, H. Sepehri Amin, K. Hono

2017 IEEE International Magnetics Conference (INTERMAG) > 1 - 2

2017 IEEE International Magnetics Conference (INTERMAG)

L1₀-ordered FePt granular thin film is the leading candidate for heat assisted magnetic recording (HAMR) media due to its high magnetocrystalline anisotropy constant (∼ 6.6 MJ/m³) that allows smaller thermally stable grain size (∼ 4 nm) [1].

chapter

Layer thickness effects and microstructure of CPP-GMR spin-valves with Ag/InZnO/Zn conductive oxide-based spacer layers

T. Nakatani, T. Sasaki, S. Li, Y. Sakuraba, more

2017 IEEE International Magnetics Conference (INTERMAG) > 1

2017 IEEE International Magnetics Conference (INTERMAG)

Improving the output of current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) sensor has been the central issue to meet the requirements for next generation read sensors.

chapter

Epitaxial magnetic tunnel junctions with a low barrier height spinel MgGa₂O₄

H. Sukegawa, Y. Kato, M. Belmoubarik, P. Cheng, more

2017 IEEE International Magnetics Conference (INTERMAG) > 1

2017 IEEE International Magnetics Conference (INTERMAG)

MgO barrier based magnetic tunnel junctions (MTJs) have drawn great attention because of their important spintronic device applications such as read heads of hard disk drives and non-volatile magnetoresistive random access memories (MRAMs).

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TEM (23)
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MAGNESIUM ALLOYS (19)
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CPP-GMR (7)
CRYSTALLIZATION (7)
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MAGNETIC RECORDING (7)
MECHANICAL PROPERTIES (7)
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HEAT ASSISTED MAGNETIC RECORDING (3)
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Search results for: K. Hono

Time domain magnetization dynamics study to estimate interlayer exchange coupling constant in Nd-Fe-B/Ni80Fe20 films

Bake-hardenable Mg–Al–Zn–Mn–Ca sheet alloy processed by twin-roll casting

Microstructure of a Dy-free Nd-Fe-B sintered magnet with 2 T coercivity

Reprint of Prospect for HRE-free high coercivity Nd-Fe-B permanent magnets

Searching the weakest link: Demagnetizing fields and magnetization reversal in permanent magnets

Effects of rolling conditions on the microstructure and mechanical properties in a Mg–Al–Ca–Mn–Zn alloy sheet

Coercivity enhancement of hot-deformed Ce-Fe-B magnets by grain boundary infiltration of Nd-Cu eutectic alloy

Improving mechanical properties and yield asymmetry in high-speed extrudable Mg-1.1Al-0.24Ca (wt%) alloy by high Mn addition

Enhancement of current-perpendicular-to-plane giant magnetoresistive outputs by improving B2-order in polycrystalline Co2(Mn0.6Fe0.4)Ge Heusler alloy films with the insertion of amorphous CoFeBTa underlayer

Micromagnetic Studies at Finite Temperature on FePt–C Granular Films

Intrinsic hard magnetic properties of Sm(Fe1−xCox)12 compound with the ThMn12 structure

A heat-treatable Mg–Al–Ca–Mn–Zn sheet alloy with good room temperature formability

Magnetization reversal of exchange-coupled and exchange-decoupled Nd-Fe-B magnets observed by magneto-optical Kerr effect microscopy

Pt surface segregation in L10-FePt nano-grains

Improved (001)-texture of FePt-C for heat-assisted magnetic recording media by insertion of Cr buffer layer

Strong and ductile age-hardening Mg-Al-Ca-Mn alloy that can be extruded as fast as aluminum alloys

Enhanced CPP-GMR effect by improved B2-order of Co₂(Mn_0.6Fe_0.4)Ge Heusler layer deposited on amorphous CoFeBTa underlayer: A quantitative estimation of site-disordering by anomalous x-ray diffraction

Origin of in-plane component for L1₀-FePt granular films deposited on MgO single crystal substrate

Layer thickness effects and microstructure of CPP-GMR spin-valves with Ag/InZnO/Zn conductive oxide-based spacer layers

Epitaxial magnetic tunnel junctions with a low barrier height spinel MgGa₂O₄

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