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We have systematically prepared diverse microstructures by annealing B-rich Fe–Si–B–Cr amorphous sheets to obtain the optimum mechanical property and cutting machinability of the alloy. Thermal, structural, and mechanical analyses showed that the early reaction sequence of the amorphous alloy upon annealing is characterized by structural relaxation, heterogeneous nucleation of the α-Fe(Si) phase at the surface, and homogeneous nucleation of metastable Fe3B core, which is enclosed by the α-Fe shell. The development of the core–shell structure, approximately 200 nm, is governed by the repeated partitioning out of Si and B from the Fe3B and α-Fe phases, respectively. The hardness and specific cutting resistance force (SCRF) were found maximum for the alloy annealed to 873 K, which is filled with the aforementioned core–shell crystalline phases. On the other hand, the best cutting performance with minimum burrs and chips, and the lowest SCRF, was realized for the alloy annealed at 763 K, which exhibits a heterogeneous microstructure, where the core–shell units are finely dispersed in the amorphous matrix.

Nanocrystalline Fe–Si–B–P–Cu alloys exhibit high saturation magnetic flux density ( B s ) and extremely low magnetic core loss ( W ), simultaneously. Low amorphous-forming ability of these alloys hinders their application potential in power transformers and motors. Here we report a solution to this problem. Minor addition of C is found to be effective in increasing the amorphous-forming ability of Fe–Si–B–P–Cu alloys. It allows fabrication of 120 mm wide ribbons (which was limited to less than 40 mm) without noticeable degradation in magnetic properties. The nanocrystalline (Fe 85.7 Si 0.5 B 9.5 P 3.5 Cu 0.8 ) 99 C 1 ribbons exhibit low coercivity ( H c )~4.5 A/m, high B s ~1.83 T and low W ~0.27 W/kg (@ 1.5 T and 50 Hz). Success in fabrication of long (60–100 m) and wide (~120 mm) ribbons, which are made up of low cost elements is promising for mass production of energy efficient high power transformers and motors

With the aim of applying to a magnetic core material, the effect of ribbon thickness on the magnetic properties of a (Fe, Co)-Si-B-P-Cu alloy ribbon was investigated. It is found that the Si addition in (Fe, Co)-Si-B-P-Cu nanocrystalline alloy increased the saturation magnetic flux density (Bs), but degraded the coercivity (Hc), suggesting that the Si addition should be suppressed to a little amount. It is also found that the replacement of Fe with Co is quite effective for obtaining better magnetic properties of Fe-Si-B-P-Cu alloy. Even for the thicker ribbons exceeding 30μm in thickness, the nanocrystalline Fe81.2Co4Si0.5B9.5P4Cu0.8 alloy exhibited low Hc of 7A/m and high Bs of 1.84T. Such excellent magnetic properties were successfully reproduced in 50mm wide ribbons. This regards that the nanocrystallized Co-containing alloy has high applicability to high-efficiency magnetic core material. [doi:10.2320/matertrans.MBW201402]

A structural heterogeneity of a newly developed soft magnetic Fe 81.2 Co 4 Si 0.5 B9.5P4Cu0.8 melt-spun alloy has been studied by transmission electron microscopy (TEM) and electron diffraction. Hollow-cone dark-field TEM imaging revealed that the density of coherent scattering regions in the as-quenched Fe 81.2 Co 4 Si 0.5 B 9.5 P 4 Cu 0.8 alloy is as high as that in the Fe 85.2 Si 2 B 8 P 4 Cu 0.8 hetero-amorphous alloy (NANOMET ® ). According to the aberration-corrected high-resolution TEM, crystalline atomic clusters, typically of ∼1 nm in diameter, are densely distributed in an amorphous matrix of Fe 81.2 Co 4 Si 0.5 B 9.5 P 4 Cu 0.8 alloy, while nanobeam electron diffraction detected weak Bragg reflections from Fe clusters with the body centered cubic structure. These results unambiguously reveal structural heterogeneity of the as-quenched Fe 81.2 Co 4 Si 0.5 B 9.5 P 4 Cu 0.8 alloy, which is similar to that observed in the NANOMET ® .

Effects of an addition of Si and P into amorphous Fe85.2B14Cu0.8 based soft magnetic alloys were investigated in boric-borate buffer solution. The addition of P decreased the passive current density effectively. Substituting Si for P in Fe85.2SixB9P5 − xCu0.8 (x = 0, 1, 2 at.%) alloys further improved corrosion resistance. After the removal of the oxide films, the passive current density was higher than those covered by the oxide films. The lowest passive current density was observed at 5 × 10− 6 A/cm2 on the Fe85.2Si1B9P4Cu0.8 alloy. On the other hand, the pitting potential of the alloys before and after removal of the oxide films was as high as about 0.96 V and was independent of chemical composition of the alloys. The addition of Si and P could enhance the corrosion resistance of Fe85.2SixB9P5 − xCu0.8 alloys via modification of the chemical composition of the oxide films. Cyclic voltammetric results indicated that the addition of Si suppressed the formation rate of bivalent Fe species, which slows down reaction rates of this rate-determining step.

The compositional dependence of metalloid elements on the as-quenched and nanocrystalline structures and soft magnetic properties in the Fe85.2SixB14-x-yPyCu0.8 melt-spun ribbons was investigated. The formation of amorphous structure in the as-quenched state was confirmed in a wide compositional range of 0 ≤ x ≤ 2 and 0 ≤ y ≤ 6 at.%. A remarkably low coercivity (7-20 A/m) is exhibited by the annealed samples having very fine (

The local structure around Cu in ${\rm Fe}_{85}{\rm Si}_{2}{\rm B}_{8}{\rm P}_{4}{\rm Cu}_{1}$ (NANOMET) and ${\rm Fe}_{85}{\rm Si}_{2}{\rm B}_{12}{\rm Cu}_{1}$ alloys was investigated by X-ray absorption fine structure (XAFS) and analytical transmission electron microscopy (TEM). The XAFS measurements indicate that the local structure around Cu atoms for the nanocrystallized ${\rm Fe}_{85}{\rm Si}_{2}{\rm B}_{8}{\rm P}_{4}{\rm Cu}_{1}$ alloy is a bcc-like structure, suggesting that Cu atoms occupy substitutional site of bcc-Fe or Cu atoms form bcc-type clusters in bcc-Fe nanocrystallites. The compositional TEM analysis indicates that Cu atoms distribute in both nanocrystallites and amorphous matrix. These facts suggest that Cu atoms in the ${\rm Fe}_{85}{\rm Si}_{2}{\rm B}_{8}{\rm P}_{4}{\rm Cu}_{1}$ alloy do not form stable fcc-Cu clusters, which act as the nucleation sites in the case of ${\rm Fe}_{73.5}{\rm Si}_{13.5}{\rm B}_{9}{\rm Nb}_{3}{\rm Cu}_{1}$ (FINEMET) alloy.

With the aim of obtain the world's biggest glassy alloy, a molten Pd 42.5 Cu 30 Ni 7.5 P 20 alloy with a total weight of 3432 g was water-quenched in a quartz tube. As a result, a cylindrical glassy alloy sample with a diameter of 80 mm and a length of 85 mm was successfully obtained. X-ray diffraction measurements for crashed fragments reveal that the obtained whole sample is vitrified into complete glassy state except for little irregular region of the bubble surface. In addition, differential scanning calorimetry measurements also reveal that the sample has quite homogeneous structure and stable thermal characteristics. In order to estimate a cooling rate for each location of the sample, finite-difference-method calculations using physical properties previously reported were carried out. The calculations exhibited good agreements with previous results and the present experimental results, verifying the validity of the calculations.

With the aim of applying to a soft-magnetic underlayer of the new type of bit-patterned media using nano-patterned glassy alloy thin film, (CoFe)–B–Si–Nb alloy thin films were deposited on a Si substrate by a DC magnetron sputtering method. The deposited thin films with the compositions of Co77Fe5B15Si2Nb1 and Co75Fe5B14Si5Nb1 were confirmed as a fully amorphous structure. The obtained Co77Fe5B15Si2Nb1 amorphous alloy thin film containing lower metalloid content exhibits extremely smooth surface and good soft-magnetic properties such as high saturation flux density of 1.2 T, in-plane low coercivity of 36 A/m, nearly zero-magnetostriction of 4 × 10−7 and high real part of permeability of 870 at 291 MHz, suggesting that the film is appropriate for the soft-magnetic underlayer. Moreover, a prototype bit-patterned media was prepared by utilizing the obtained thin film as a soft-magnetic underlayer. As a result of static tester measurements with a commercial perpendicular magnetic head, accurate information reading and writing on the prototype bit-patterned media were confirmed. It is therefore said that the Co77Fe5B15Si2Nb1 amorphous alloy thin film is a candidate material for the soft-magnetic underlayer of the new type of bit-patterned media.

With the aim of preparing nano-scale pattern for micro-machines and nano-devices, fabrication and imprint ability of Pd39Cu29Ni13P19 glassy alloy thin film were investigated. By using a magnetron sputtering method, the Pd-based glassy alloy thin film of 1 μm in thickness was successfully fabricated. The Pd-based glassy alloy thin film shows large supercooled liquid region, long incubation time to crystallization, high hardness and very smooth surface, which are suitable for nano-imprint processing. Nano-imprint ability of the obtained film is demonstrated by using dot array mold with a dot diameter of 30 nm. The imprinted hole array pattern precisely corresponded to the periodic dot pattern of the mold. These results suggest that the Pd-based glassy alloy thin film has high potential for application to the nano-imprinting materials for micro-machines and nano-devices.

With the aim of developing a novel preparation process for bit-patterned-media, nano-patterned glassy alloy composite composed of zero-magneto-striction Co–Fe–B amorphous alloy thin film, Pd–Cu–Ni–P glassy alloy and Co/Pd multi-layer with perpendicular magnetization was prepared. Using the commercial imprinting mold, periodic nano hole array with a hole diameter of 90 nm and a pitch of 180 nm was successfully prepared on the surface of Pd-based glassy alloy thin film. By overlaying the Co/Pd multi-layer with perpendicular magnetization and surface polishing, isolated Co/Pd magnetic dots embedded into nano hole array can be obtained. These magnetic dots act as single magnetic domains. In addition, the change in magnetization direction was confirmed under magnetic fields of ±20 kOe. These results suggest that the glassy alloy nano-composite is suitable for BPM of high data density HDD. It is therefore concluded that the preparation method is candidate process for the preparation of BPM of high data density HDD.

With the aim of preparing nano-hole array for bit patterned media of ultra high density data storage, fabrication and imprint-ability of Pd–Cu–Ni–P glassy alloy thin film was investigated. By using a pulsed-laser deposition method, the Pd-based glassy alloy thin film was successfully fabricated. The thermal characteristics of the obtained film were very close to those of the melt-spun glassy alloy ribbon. The obtained film has very smooth surface and high hardness, which are suitable for nano-imprint processing. Nano-imprint-ability of the obtained film is demonstrated by using dot array mold with a dot diameter of 30 nm. The periodic dot pattern of the mold was precisely transcribed. These results suggest that the Pd–Cu–Ni–P glassy alloy thin films are potential nano-imprinting materials for fabricating bit patterned media.

Chemically ordered hard magnetic L10-FeNi phase of higher grade than cosmic meteorites is produced artificially. Present alloy design shortens the formation time from hundreds of millions of years for natural meteorites to less than 300 hours. Electron diffraction detects four-fold 110 superlattice reflections and a high chemical order parameter (S "Equation missing" 0.8) for the developed L10-FeNi phase. The magnetic field of more than 3.5 kOe is required for the switching of magnetization. Experimental results along with computer simulation suggest that the ordered phase is formed due to three factors related to the amorphous state: high diffusion rates of the constituent elements at lower temperatures when crystallizing, a large driving force for precipitation of the L10 phase and the possible presence of L10 clusters. Present results can resolve mineral exhaustion issues in the development of next-generation hard magnetic materials because the alloys are free from rare-earth elements and the technique is well suited for mass production.

With the aim of developing a new bulk glassy alloy which can be applied to biomedical applications, we examined glass-forming ability and mechanical properties of Ni-free glassy alloys in Pd 5 0 - x Pt x Cu 3 0 P 2 0 system.As a result, the best glass-forming composition is located at Pd 3 5 Pt 1 5 Cu 3 0 P 2 0 , and the alloy can be formed into bulk glassy rods with diameters of up to at least 30mm by fluxed water quenching. For the bulk glassy alloy, fracture strength, fracture elongation and Young's modulus were measured to be 1590 MPa, 1.8% and 99.8 GPa, respectively, under a compressive stress and 1410 MPa, 1.7% and 83.0 GPa, respectively, under a tensile stress. These features of high glass-forming ability and good mechanical properties are expected to be used as biomedical materials.

In order to realize biomedical applications of bulk glassy alloys, we have developed new Pd-based glassy alloys with Ni-free composition in Pd-Pt-Cu-P system and it is revealed that the highest glass-forming ability is obtained at a composition of Pd 35 Pt 15 Cu 30 P 20 . In addition the alloy can be formed into bulk glassy rods with diameters of up to at least 30 mm by fluxed water quenching. In order to clarify the critical cooling rate for glass-formation, undercooling behavior and crystal growth rate are also discussed. Crystallization of the alloy under continuous cooling is mainly dominated by surface nucleation. Apparent crystal growth rate of the alloy at 0.73 T m is evaluated to be 5.2 x 10 -6 m·s -1 and this value is four orders of magnitude higher than that of previous Pd 40 Cu 30 Ni 10 P 20 at the same degree of undercooling.

In this paper, we study the domain wall dynamics in high magnetic flux density (–1.85 T) of soft magnetic ribbons Fe81.2Co4Si0.5B9.5P4Cu0.8 prepared with various annealing conditions. It is observed that annealing these ribbons beyond a temperature (C) crystalizes the alloy with the appearance of α-Fe(-Co) phase. The post annealing leads to a change from amorphous to nanocrystalline phase accompanied by a reduction in internal stress in the ribbons. Domain imaging has been performed under both dc and ac fields to study the domain wall behavior in these ribbons. A wide variety of domain structures are observed in ribbons prepared with different annealing temperature as a result of the change in the intrinsic anisotropy. Under an ac magnetic field, the 'stress patterns' in the amorphous ribbons are robust. However, ribbons with reduced stress (i.e. nanocrystalline) exhibit domain wall propagation which hints at a significant reduction in magnetocrystalline and magnetoelastic anisotropies due to uniform nanocrystallization. The ribbon annealed at C exhibits static domain patterns resulting from strong pinning centers created by Fe-B precipitates.

In order to clarify detailed surface morphologies and cross sectional nano-structures of novel prototype bit-patterned-medias using nano-imprinted glassy alloy thin films, observations using scanning and transmission electron microscopes were carried out. By employing a focused ion beam milling with an extra low energy, the delicate and fragile structures of samples were successfully maintained and protected during sample preparations. The sequential observations of the preparation process reveal that Co/Pd multilayer is embedded into the imprinted glassy alloy thin film nano hole array with a hole diameter of 30 nm, and the embedded Co/Pd multilayer as acting magnetic recording dots is isolated each other. Using the obtained results, technological and productive feasibility of the prototype BPM as a next generation HDD with a data density above 2 Tbit/inch 2 is also discussed.

With the aim of applying to a soft magnetic underlayer of the double-layered perpendicular magnetic recording media, an Fe 74.9 B 17.5 Si 2.5 Nb 5.1 alloy thin film was fabricated on Si substrate by a pulsed laser deposition method. The Fe-based alloy thin film of 200 nm in thickness was confirmed as a glassy structure. The thermal properties of the thin film have similar features to those for the melt-spun glassy alloy ribbon. The glassy alloy thin film exhibits good soft magnetic properties, i.e., high B s of 1.2 T and in-plane low H c of 134 A/m. The Fe–B–Si–Nb glassy alloy thin film is expected to be suitable for the soft magnetic underlayer material in the double-layered perpendicular magnetic recording media.

In order to realize biomedical applications of bulk glassy alloys, we have developed new Pd-based glassy alloys with Ni-free composition in the Pd–Pt–Cu–P system. As a result, it is revealed that the highest glass-forming ability is obtained at the composition of Pd 35 Pt 15 Cu 30 P 20 . Furthermore, the alloy can be formed into bulk glassy rods with diameters of up to at least 30 mm by fluxed water quenching. In this paper, we intend to clarify undercooling behavior and critical cooling rate for glass-formation in the new bulk glassy Pd 35 Pt 15 Cu 30 P 20 alloy.

Size of the clusters and structure details of fcc Cu clusters in nanocrystalline soft magnetic alloy of Fe85-86Si1-2B8P4Cu1 (NANOMET) are investigated. A linear combination fitting of XAFS data indicates that about 30% of Cu atoms are partitioned in the fcc clusters and the rest in the amorphous matrix. EXAFS of the fcc Cu nanocluster embedded in amorphous matrix is calculated on the basis of a simple fcc structure model using FEFF9. Surface effect of the nanoclusters is considered by counting a fraction of the nearest neighbour atoms in amorphous matrix. Good agreement with the experimental result is obtained for the fcc nanocluster with 9 coordination shells which consists of total 177 atoms within 1.5 nm in a diameter.

Kazuhisa Sato, Parmanand Sharma, Yan Zhang, Kana Takenaka, and Akihiro Makino, "Crystallization induced ordering of hard magnetic L1₀ phase in melt-spun FeNi-based ribbons", AIP Advances 6, 055218 (2016) https://doi.org/10.1063/1.4952968., The microstructure of newly developed hard magnetic Fe₄₂Ni₄₁.₃SixB₁₂-xP₄Cu₀.₇ (x = 2 to 8 at%) nanocrystalline alloy ribbons has been studied by transmission electron microscopy (TEM) and electron diffraction. A high-density polycrystalline grains, ∼30 nm in size, were formed in a ribbon after annealing at 673 K for 288 hours. Elemental mapping of the annealed specimen revealed the coexistence of three regions, Fe-rich, Ni-rich, and nearly equiatomic Fe-Ni, with areal fractions of 37%, 40%, and 23 %, respectively. The equiatomic L1₀-type ordered phase of FeNi was detected in between the Fe and Ni-rich phases. The presence of superlattice reflections in nanobeam electron diffraction patterns confirmed the formation of the hard magnetic L1₀ phase beyond any doubt. The L1₀ phase of FeNi was detected in alloys annealed in the temperature range of 673 to 813 K. The present results suggest that the order-disorder transition temperature of L1₀ FeNi is higher than the previously reported value (593 K). The high diffusion rates of the constituent elements induced by the crystallization of an amorphous phase at relatively low temperature (∼673K) are responsible for the development of atomic ordering in FeNi.

With the aim of investigating nano-imprintability of glassy alloys in a film form, Zr(49)Al(11)Ni(8)Cu(32), Pd(39)Cu(29)Ni(13)P(19) and Cu(38)Zr(47)Al(9)Ag(6) glassy alloy thin films were fabricated on Si substrate by a magnetron sputtering method. These films exhibit a very smooth surface, a distinct glass transition phenomenon and a large supercooled liquid region of about 80 K, which are suitable for imprinting materials. Moreover, thermal nano-imprintability of these obtained films is demonstrated by using a dot array mold with a dot diameter of 90 nm. Surface observations revealed that periodic nano-hole arrays with a hole diameter of 90 nm were successfully imprinted on the surface of these films. Among them, Pd-based glassy alloy thin film indicated more precise pattern imprintability, namely, flatter residual surface plane and sharper hole edge. It is said that these glassy alloy thin films, especially Pd-based glassy alloy thin film, are one of the promising materials for fabricating micro-machines and nano-devices by thermal imprinting.

With the aim of investigating fundamental properties and nano-imprintabilities of glassy alloy in the film form, Zr49Al11Ni8Cu32, Pd39Cu29Ni13P19 and Cu38Zr47Al9Ag6 alloy thin films were fabricated on Si substrate by a magnetron sputtering method. These thin films exhibit distinct glass-tradition phenomenon and large supercooled liquid region of about 80 K, confirming as a glassy structure and have very smooth surface and sufficient hardness to maintain imprinted shape, which are suitable for nano-imprint processing. Moreover, thermal nano-imprintabilies of these obtained films are demonstrated by using a dot array mold with a dot diameter of 90 nm and a pitch of 180 nm. Surface observations revealed that periodic nano-hole arrays were successfully imprinted on the surface of these films and precisely corresponded to the periodic dot pattern of the mold. Particularly, Pd-based glassy alloy thin film indicated more precise pattern imprintability, namely, more flat residual surface plane and sharper hole edge. These results suggest that these glassy alloy thin films, especially Pd-based glassy alloy thin film have high potential for application to the nano-imprinting materials.

Present progress in developments of glassy alloy composites for bit-patterned-media and non-equilibrium Cu-based alloys for conductive materials of electrical connectors are reviewed. It is proven that the imprinting of the Pd-based glassy alloy thin film is favorable for the formation of nano-structured devices. Detailed imprinted morphologies formed by different imprinting conditions were examined. In addition, technology of large area imprinting up to 2.5 inches area has been successfully developed and it is now available for production. These technological developments will be utilized for next generation bit-patterned-media with high data density. A newly developed non-equilibrium Cu-Zr-Ag alloy was prepared into sheet form by the combination of casting, cold rolling and annealing. The alloy sheet exhibited high tensile strength of exceeding 1500 MPa and good electrical conductivity of 30% IACS. However, bending ductility should be improved for the actual production of connector. Through the several examinations, remaining issues that should be solved are discussed in the framework of industrialization and commercialization. These obtained results suggest that the glassy alloy composite or non-equilibrium alloy designed by the glass-forming rules have a great potential to develop innovative products in the near future.

It is known that Cu plays an essential role in reducing the grain size of precipitated bcc Fe(Si) nanocrystallites in a nanocrystalline soft-magnetic Fe85.2Si1B9P4Cu0.8 (NANOMET®) alloys like as an Fe73.5Si13.5B9Nb3Cu1 (FINEMET®). However, significant differences are there between two alloys; NANOMET has much higher iron content (∼85%) than FINEMET (73.5%) and the former contains P instead of Nb for the latter. In the present work, the local structure around Cu in FINEMET was measured by X-ray absorption fine structure (XAFS) at 20 K and compared with those of NANOMET during nanocrystallization. Definite differences between NANOMET and FINEMET are found in the way of the evolution of Cu clusters during nanocrystallization. In FINEMET, an fcc structure of Cu is recognized in an as-quenched ribbon indicating existence of a small number of Cu clusters or a very small size of Cu clusters which is stable up to 450 °C, while the fcc Cu clusters are developed rapidly above 450 °C. An fcc structure of the Cu clus...

Fe-based Fe85B15, Fe84B15Cu1, Fe82Si2B15Cu1, Fe85Si2B12Cu1, and Fe85Si2B8P4Cu1 (NANOMET®) alloys were experimental and computational analyzed to clarify the features of NANOMET that exhibits high saturation magnetic flux density (Bs) nearly 1.9 T and low core loss than conventional nanocrystalline soft magnetic alloys. The X-ray diffraction analysis for ribbon specimens produced experimentally by melt spinning from melts revealed that the samples were almost formed into an amorphous single phase. Then, the as-quenched samples were analyzed with differential scanning calorimeter (DSC) experimentally for exothermic enthalpies of the primary and secondary crystallizations (ΔHx1 and ΔHx2) and their crystallization temperatures (Tx1 and Tx2), respectively. The ratio ΔHx1/ΔHx2 measured by DSC experimentally tended to be extremely high for the Fe85Si2B8P4Cu1 alloy, and this tendency was reproduced by the analysis with commercial software, Thermo-Calc, with database for Fe-based alloys, TCFE7 for Gibbs free energ...

Here, the authors fabricated a mold consisting of nanodot arrays with an 18-nm pitch and performed nanoimprinting of metallic glass for developing bitpatterned media (BPM) with an areal recording density of 2 Tbit/in.2. Specifically, they investigated the feasibility of SiO2/Si mold fabrication by metal mask patterning with focused ion beam assisted chemical vapor deposition (FIB-CVD) and reactive ion etching (RIE). SiO2 was etched with a mixed gas of CHF3 and O2, resulting in successful fabrication of convex nanodot arrays with an 18-nm pitch. The authors attempted nanoimprinting of Pd-based metallic glass with the fabricated SiO2 mold and clearly confirmed the replication of the fine nanohole pattern. These results suggest that the proposed FIB-CVD and RIE process is a promising method for fabricating ultrafine nanodot arrays and that metallic glasses are excellent nanoimprintable materials for mass-produced nanodevices such as BPM with ultrahigh recording density.