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1 May 2010

Volume 107, Issue 9, Articles (09xxxx)

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back to top Soft Magnetic Materials and Domains

Magnetic behavior of rapidly quenched submicron amorphous wires

H. Chiriac, S. Corodeanu, M. Lostun, G. Ababei, and T.-A. Óvári

J. Appl. Phys. 107, 09A301 (2010); http://dx.doi.org/10.1063/1.3334168 (3 pages) | Cited 14 times

Online Publication Date: 12 April 2010

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Results on the magnetic behavior of glass-coated amorphous wires with metallic nucleus diameters in the submicron range are reported for the first time. The magnetic behavior of nearly zero magnetostrictive submicron amorphous wires is different from that observed in amorphous microwires with typical dimensions and similar composition. Submicron wires are bistable, whereas typical microwires show an almost anhysteretic loop. Bistability of submicron wires is maintained even in a very thin surface layer, which was shown to display a helical magnetic anisotropy. The origin of this specific behavior is the shape anisotropy which becomes dominant at lower dimensions of the metallic nucleus. The study of submicron amorphous wires opens up the way for new applications of amorphous wires.
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75.80.+q Magnetomechanical effects, magnetostriction
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.78.-n Magnetization dynamics
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Kj Amorphous and quasicrystalline magnetic materials

Nonclassical crystallization of amorphous iron nanoparticles by radio frequency methods

K. J. Carroll, J. A. Pitts, Kai Zhang, A. K. Pradhan, and E. E. Carpenter

J. Appl. Phys. 107, 09A302 (2010); http://dx.doi.org/10.1063/1.3334169 (3 pages) | Cited 2 times

Online Publication Date: 15 April 2010

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Amorphous iron nanoparticles were synthesized using an aqueous reduction in iron(II) sulfate with sodium borohydride and sodium citrate. Various radio frequency (rf) exposure times were investigated in order to determine trends in nonclassical crystallization. RF times from 15 to 300 s revealed an increase in crystallite size from 5 to 60 nm, as determined by powder x-ray diffraction. Also, solvent optimization revealed that ethanol produced the largest trends for increasing crystallite size without total oxidation of the samples. Magnetic characterization by room temperature vibrating sample magnetometry and high resolution transmission microscopy was performed to verify magnetic properties and particle morphology.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
64.70.dg Crystallization of specific substances

Annealing of amorphous FexCo100−x nanoparticles synthesized by a modified aqueous reduction using NaBH4

K. J. Carroll, D. M. Hudgins, L. W. Brown, S. D. Yoon, D. Heiman, V. G. Harris, and E. E. Carpenter

J. Appl. Phys. 107, 09A303 (2010); http://dx.doi.org/10.1063/1.3334172 (3 pages) | Cited 3 times

Online Publication Date: 15 April 2010

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FexCo100−x nanoparticles were synthesized by aqueous reduction in iron (II) sulfate and cobalt (II) sulfate using sodium borohydride and sodium citrate. The initial concentrations of iron and cobalt were varied while maintaining an overall metal concentration of 4.60 mM. Increasing the cobalt content from 0 to 100 at. % decreased the magnetization saturation from 152 to 48 emu/g, as determined by room temperature vibrating sample magnetometry. Annealing the samples at 450 and 600 °C showed an increase in crystallite size. Powder x-ray diffraction and transmission electron microscopy was performed to determine the phases and morphology of the materials.
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81.07.Bc Nanocrystalline materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
61.72.Cc Kinetics of defect formation and annealing
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Observations of oxidation mechanisms and kinetics in faceted FeCo magnetic nanoparticles

N. J. Jones, K. L. McNerny, A. T. Wise, M. Sorescu, M. E. McHenry, and D. E. Laughlin

J. Appl. Phys. 107, 09A304 (2010); http://dx.doi.org/10.1063/1.3334197 (3 pages) | Cited 2 times

Online Publication Date: 15 April 2010

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(Fe50Co50)97V2Nb1 nanoparticles were synthesized in an induction plasma torch and oxidized isochronally at temperatures between room temperature (RT) and 900 °C. The particles exhibited three stages of oxidation present at different temperatures. The initial oxide layer was nearly Co-free, beginning at 3 nm at RT, and Co appeared to oxidize separately from the iron. Iron cations were determined to be the mobile species during oxidation, yielding a progressively more Co-rich core as oxidation progressed, decreasing from an average diameter of 42 to 25 nm, while the oxide tripled in size. At 350 °C, the particles exhibited a less dense core, and at 900 °C the particles were observed to have changed morphology completely with some sintering, forming completely oxidized particles with an average diameter three times the as received size.
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81.16.Pr Micro- and nano-oxidation
81.65.Mq Oxidation
75.50.Tt Fine-particle systems; nanocrystalline materials
81.07.Bc Nanocrystalline materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Metastable γ-FeNi nanostructures with tunable Curie temperature

K. J. Miller, M. Sofman, K. McNerny, and M. E. McHenry

J. Appl. Phys. 107, 09A305 (2010); http://dx.doi.org/10.1063/1.3334198 (3 pages) | Cited 5 times

Online Publication Date: 15 April 2010

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We report on new metastable γ-FeNi nanoparticles produced by mechanical alloying of melt-spun ribbon using a high energy ball mill followed by a solution annealing treatment in the γ-phase region and water quenching in of the face-centered cubic γ-phase. In the Fe–Ni phase diagram there is a strong compositional dependence of the Curie temperature, Tc, on composition in the γ-phase. This work studies the stabilization of γ-phase nanostructures and the compositional tuning of Tc in Fe–Ni alloys which can have important ramifications on the self-regulated heating of magnetic nanoparticles in temperature ranges of interest for applications in polymer curing and cancer thermotherapies. To date we have achieved Curie temperatures as low as 120 °C by this method.
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81.20.Wk Machining, milling
81.07.Bc Nanocrystalline materials
61.46.-w Structure of nanoscale materials
61.72.Cc Kinetics of defect formation and annealing
81.30.Bx Phase diagrams of metals, alloys, and oxides

Preparation and structural characterization of FeCo epitaxial thin films on insulating single-crystal substrates

Tsutomu Nishiyama (西山努), Mitsuru Ohtake (大竹充), Fumiyoshi Kirino (桐野文良), and Masaaki Futamoto (二本正昭)

J. Appl. Phys. 107, 09A306 (2010); http://dx.doi.org/10.1063/1.3334200 (3 pages) | Cited 1 time

Online Publication Date: 15 April 2010

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FeCo epitaxial films were prepared on MgO(111), SrTiO3(111), and Al2O3(0001) single-crystal substrates by ultrahigh vacuum molecular beam epitaxy. The effects of insulating substrate material on the film growth process and the structures were investigated. FeCo(110)bcc films grow on MgO substrates with two type domains, Nishiyama–Wassermann (NW) and Kurdjumov–Sachs (KS) relationships. On the contrary, FeCo films grown on SrTiO3 and Al2O3 substrates include FeCo(111)bcc crystal in addition to the FeCo(110)bcc crystals with NW and KS relationships. The FeCo(111)bcc crystal consists of two type domains whose orientations are rotated around the film normal by 180° each other. The out-of-plane and the in-plane lattice spacings of FeCo(110)bcc and FeCo(111)bcc crystals formed on the insulating substrates are in agreement with those of the bulk Fe50Co50 (at. %) crystal with small errors ranging between +0.2% and +0.4%, showing that the strains in the epitaxial films are very small.
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68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.15.Aa Theory and models of film growth

The effect of precipitate size on magnetic domain behavior in grain-oriented electrical steels

Steven Turner, Anthony Moses, Jeremy Hall, and Keith Jenkins

J. Appl. Phys. 107, 09A307 (2010); http://dx.doi.org/10.1063/1.3334201 (3 pages) | Cited 1 time

Online Publication Date: 19 April 2010

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Precipitates in the form of grain growth inhibitors play an essential role in the production of grain-oriented electrical steels, as they promote the development of Goss texture during secondary recrystallization. However, the presence of precipitates in the final material can have a detrimental effect on loss and permeability, as they impede domain wall motion during the magnetization process. In previous work [ K. Jenkins and M. Lindenmo, J. Magn. Magn. Mater. 320, 2423 (2008) ], a conventional grain-oriented electrical steel was presented that contained very fine precipitates, which did not damage the bulk magnetic properties. In this article the influence of precipitate size is investigated by comparing local Barkhausen noise measurements and electron backscatter diffraction analysis for a number of grain-oriented electrical steels, which are metallurgically similar except for the size and abundance of precipitates.
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75.60.Ch Domain walls and domain structure
82.70.-y Disperse systems; complex fluids
68.35.B- Structure of clean surfaces (and surface reconstruction)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetostriction and effective magnetic anisotropy of Co-contained Finemet nanocrystalline alloys

Zhi Wang, Jing Yang, Ye-mei Han, Dong-xu Zhang, Bin Fu, and Rong-chang Ye

J. Appl. Phys. 107, 09A308 (2010); http://dx.doi.org/10.1063/1.3340514 (3 pages) | Cited 9 times

Online Publication Date: 19 April 2010

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The microstructure and magnetic properties of Co-contained Finemet nanocrystalline alloys were investigated. By contrasting with Finemet, the Co-contained Finemet nanocrystalline alloys have a broad temperature range for precipitating a single α-FeCo crystalline phrase and a relatively higher Curie temperature of amorphous phase. After full nanocrystallization they exhibit improved high-temperature soft magnetic properties. However the room-temperature permeability of Co-contained Finemet was obviously lower than that of Finemet. For clarifying the reason, the effective magnetic anisotropy 〈K〉 and the saturation magnetostriction λs were measured, respectively, and the 〈K〉 of Co-contained Finemet is about 100–137 J/m3, which is the same order of magnitude as Finemet, but the λs of Co-contained Finemet-type alloy is much higher than that of Finemet which results in a relatively lower permeability.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.50.Kj Amorphous and quasicrystalline magnetic materials
81.30.Mh Solid-phase precipitation

Micromagnetic study of magnetic domains in platelets with perpendicular uniaxial anisotropy

Ben Van de Wiele, Luc Dupré, and Daniël De Zutter

J. Appl. Phys. 107, 09A309 (2010); http://dx.doi.org/10.1063/1.3348265 (3 pages)

Online Publication Date: 19 April 2010

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This paper studies the domain configurations in platelets with perpendicular uniaxial anisotropy. Due to the large sample dimensions, one typically relies on the domain theory to describe the domain patterns. The growing computer resources make it however possible to perform full micromagnetic simulations on the domain scale. We compare the domain configurations obtained from micromagnetic simulations with those predicted by different domain theory models for a varying anisotropy strength Ku. It is found that the Landau structure is valid for small Ku, while the open Landau–Kittel structure only poorly describes the closure domains for higher Ku. The model proposed by Hubert, enabling closure domains with a tilted magnetization angle is the most accurate.
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75.78.Cd Micromagnetic simulations
75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.60.Ch Domain walls and domain structure
75.30.Gw Magnetic anisotropy

Magnetic field induced enhancement in thermal conductivity of magnetite nanofluid

Kinnari Parekh and Hyo Sook Lee

J. Appl. Phys. 107, 09A310 (2010); http://dx.doi.org/10.1063/1.3348387 (3 pages) | Cited 10 times

Online Publication Date: 19 April 2010

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Magnetite nanofluid is synthesized using continuous chemical process. Powder x-ray diffraction and transmission electron microscopy show single phase spinel structure with size of 9.83 and 9.9 nm, respectively. Thermal conductivity of magnetite nanofluid has been studied as a function of transverse magnetic field and temperature. We found almost 30% enhancements in thermal conductivity for 4.7% volume fraction under transverse magnetic field. This result is explained on the basis of formation of continuous three-dimensional zipperlike structure of magnetic nanoparticles inside magnetic fluid. The temperature dependent thermal conductivity shows no enhancement in the temperature region of 25–65 °C.
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66.25.+g Thermal conduction in nonmetallic liquids
75.50.Mm Magnetic liquids
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.-c Magnetic properties of nanostructures
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.50.Dd Nonmetallic ferromagnetic materials

Minimizing oxygen inclusion when electroplating high saturation density CoFe for microelectromechanical system

Jue Chen, Eva Flick, and Hans H. Gatzen

J. Appl. Phys. 107, 09A311 (2010); http://dx.doi.org/10.1063/1.3348501 (3 pages)

Online Publication Date: 19 April 2010

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Co–Fe alloys with a high saturation flux density Bs are used as soft magnetic materials in various microelectromechanical system applications. The electroplating process to deposit this material was widely researched. This paper describes experimental investigations to optimize the Co–Fe electroplating process. Besides the high saturation flux density Bs and other magnetic properties, mechanical and chemical properties like low film stress and good corrosion resistance also have to be considered. In these experiments, test electrolytes with different additives were used. The main purpose of those additives is to avoid the oxidation of Fe2+ to Fe3+ in the electrolyte to minimize the formation of Fe(OH)3 and its integration in the deposited film. Vibrating sample magnetometer measurements were applied to characterize the magnetic properties. The composition of Fe and Co in the deposited film was determined by energy dispersive x-ray spectroscopy. An electron probe microanalyzer was used to determine the impurities (O, S, and B) in the deposits. The results show different efficiencies of the applied additives improving the plating process.
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81.15.Pq Electrodeposition, electroplating
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.de Elastic moduli
62.20.dj Poisson's ratio
75.70.-i Magnetic properties of thin films, surfaces, and interfaces

Chemical synthesis of monodisperse γ-Fe–Ni magnetic nanoparticles with tunable Curie temperatures for self-regulated hyperthermia

K. L. McNerny, Y. Kim, D. E. Laughlin, and M. E. McHenry

J. Appl. Phys. 107, 09A312 (2010); http://dx.doi.org/10.1063/1.3348738 (3 pages) | Cited 6 times

Online Publication Date: 19 April 2010

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Magnetic nanoparticles (MNPs) possessing low Curie temperatures (TC’s) offer the possibility for self-regulated heating of cancer cells, where the TC acts as an upper limit to heating to prevent damage to neighboring healthy tissue. We report the synthesis of monodisperse metastable fcc γ-phase Fe–Ni MNPs possessing tunable TC’s, whose stoichiometries have been predicted from metastable extensions to an equilibrium Fe–Ni phase diagram. Metastable alloys have been predicted within the constructs of the T0 construction in the Fe–Ni eutectoid phase diagram. Fe–Ni MNPs have been synthesized via chemical reduction in Fe- and Ni-precursors with stoichiometries ranging from Fe90Ni10 to Fe70Ni30. Mn-precursors have been added to further reduce the alloy’s TC. MNP morphology and structure have been confirmed by x-ray diffraction and transmission electron microscopy while magnetic properties were investigated using vibrating sample magnetometry. Fe70Ni30 MNPs were found to have a TC of 82 °C and specific magnetization of 66 emu/g. Addition of 1 wt % Mn to Fe75Ni25 reduced the TC to 78 °C, which is the lowest reported for fcc Fe–Ni alloys. We also report a model for radio frequency self-regulated heating, in which the maximum achievable temperature of water-MNP suspensions (TC<100 °C) or octyl ether-MNP suspensions (TC>100 °C) is approximately the TC of the MNPs suspended in the solution.
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75.75.Cd Fabrication of magnetic nanostructures
81.07.Bc Nanocrystalline materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Fe–Co–Cr nanocomposites for application in self-regulated rf heating

K. J. Miller, A. Colletti, P. J. Papi, and M. E. McHenry

J. Appl. Phys. 107, 09A313 (2010); http://dx.doi.org/10.1063/1.3349043 (3 pages) | Cited 5 times

Online Publication Date: 19 April 2010

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Fe–Co–Cr alloys have been developed with a Curie temperature, Tc, appropriate for ferrofluid cooling and self-regulated heating applications. These alloys have low Curie temperatures, moderate magnetic moments and provide increased heat capacity in a liquid used in a thermal cycle. Amorphous powders have been synthesized by cryo-SPEX milling melt-spun ribbons at 77 K. Transmission electron microscopy reveals cryomilled magnetic nanoparticles (MNPs) with a mean diameter of 4.2 nm to form agglomerates ∼ 30 nm in size. Vibrating sample magnetometer and superconducting quantum interference device magnetometry of amorphous powders reveal a specific magnetization, σs, of 104 emu/g at 4 K in a 300 mT field and a Tc of 335 K. Nanoparticles were suspended in ferrofluids by ultrasonication with a Pluronic F127 surfactant to stabilize them in aqueous solution. Ferrofluids of varying MNP concentration were rf heated in a 27.2 mT field at 267 kHz. For 1.24 vol % of MNPs in the ferrofluid, a solution reached temperatures>50 °C in ∼ 70 s, and showed Curie-limiting temperature behavior at ∼ 75 °C. These results demonstrate self-limited heating of FeCoCr MNPs at 75 °C which may have application in polymer curing.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Mm Magnetic liquids
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Novel magnetic microwires-embedded composites for structural health monitoring applications

F. X. Qin, N. Pankratov, H. X. Peng, M. H. Phan, L. V. Panina, M. Ipatov, V. Zhukova, A. Zhukov, and J. Gonzalez

J. Appl. Phys. 107, 09A314 (2010); http://dx.doi.org/10.1063/1.3350897 (3 pages) | Cited 13 times

Online Publication Date: 19 April 2010

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We report the results of a systematic study of the magnetic, mechanical, magnetoimpedance and field tunable properties of glass-coated amorphous Co68.7Fe4Ni1B13Si11Mo2.3 microwires and composites containing these microwires. The magnetic microwires possess good magnetic and mechanical properties. The magnetoimpedance ratio in the gigahertz range varies sensitively with applied fields below the anisotropy field but becomes unchanged for higher applied fields. The good mechanical properties are retained in the magnetic microwires-embedded composites. The strong field dependences of the effective permittivity and transmission parameters in the gigahertz range indicate that the present composites are very promising candidate materials for structural health monitoring and self-sensing applications.
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75.30.Gw Magnetic anisotropy
77.22.Ch Permittivity (dielectric function)
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.F- Deformation and plasticity
75.50.Bb Fe and its alloys
75.50.Kj Amorphous and quasicrystalline magnetic materials

Enhanced glass-forming ability of FeCoBSiNb bulk glassy alloys prepared using commercial raw materials through the optimization of Nb content

Ying Fu, Baolong Shen, Hisamichi Kimura, Akihiro Makino, and Akihisa Inoue

J. Appl. Phys. 107, 09A315 (2010); http://dx.doi.org/10.1063/1.3350898 (3 pages) | Cited 3 times

Online Publication Date: 19 April 2010

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We optimized the alloy compositions by modifying the Nb content in [(Fe0.5Co0.5)0.75B0.20Si0.05]100−xNbx(x = 3.6–4.4) alloy system. As a result, it was found that the Nb content of 4.3 at. % was effective for approaching alloy to a eutectic point. By copper mold casting, [(Fe0.5Co0.5)0.75B0.20Si0.05]95.7Nb4.3 bulk glassy alloy rods with diameters up to 4 mm were successfully synthesized even using commercial raw materials. These glassy alloys exhibit a rather high saturation magnetization of 0.77 T and low coercive force of 2.5 A/m.
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61.43.Fs Glasses
64.70.pe Metallic glasses
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.50.Bb Fe and its alloys
81.05.Kf Glasses (including metallic glasses)

Increased induction in FeCo-based nanocomposite materials with reduced early transition metal growth inhibitors

K. J. Miller, A. Leary, S. J. Kernion, A. Wise, D. E. Laughlin, M. E. McHenry, Vladimir Keylin, and Joe Huth

J. Appl. Phys. 107, 09A316 (2010); http://dx.doi.org/10.1063/1.3350900 (3 pages) | Cited 5 times

Online Publication Date: 19 April 2010

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We report on new high-saturation induction, high-temperature nanocomposite alloys with reduced glass formers. The amounts of the magnetic transition metals and early transition metal growth inhibitors were systematically varied to determine trade-offs between higher inductions and fine microstructures with consequently lower magnetic losses. Alloys of nominal composition (Fe65Co35)79.5+xNb4−xB13Si2Cu1.5 (x = 0–4) were cast into a 28 mm wide, 20 μm thick ribbon from which toroidal cores were wound. Inductions and magnetic losses were measured after nanocrystallization and stress relief. We report technical magnetic properties: permeability, maximum induction, remanence ratio, coercive field, and high frequency magnetic losses as a function of composition and annealing temperature for these alloys. Of note is the development of maximum inductions in excess of 1.76 T in cores made of alloys with the x = 4 composition and maximum inductions in excess of 1.67 T in alloys with the x = 3 composition, which also exhibit power losses smaller than 10 W/kg at 0.2 T induction levels in 20 kHz fields. We discuss optimization of induction with chemistry and correlate the microstructures with losses.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.75.Cd Fabrication of magnetic nanostructures
81.07.Bc Nanocrystalline materials
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.78.-n Magnetization dynamics

Magnetoresistance effect in soft magnetic amorphous microwires

T.-A. Óvári, M. Grigoraş, and H. Chiriac

J. Appl. Phys. 107, 09A317 (2010); http://dx.doi.org/10.1063/1.3356226 (3 pages) | Cited 2 times

Online Publication Date: 20 April 2010

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Results on the magnetoresistance (MR) effect in Co-based amorphous glass-coated microwires with nearly zero magnetostriction and no granular structure are reported. MR measurements have been performed in parallel and perpendicular configurations, in both low field and high field regimes. The results show that high field resistance variations are caused by the corresponding magnetization processes in both parallel and perpendicular configurations. In case of low parallel field, no resistance variation has been emphasized. A sharp MR response was observed in case of a perpendicularly applied low field and it was attributed to the interdomain wall between the inner core and the outer shell of such microwires. The sharpness of the low field MR peak can be controlled through the microwire dimensions. The results bring new information about the domain structure of amorphous microwires and open up new application opportunities for these materials.
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75.47.Np Metals and alloys
75.80.+q Magnetomechanical effects, magnetostriction
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.60.Ch Domain walls and domain structure
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Effect of reactive gas (oxygen/chlorine/fluorine) etching on the magnetic flux of a high moment write pole material

Jinqiu Zhang, Feng Liu, Lifan Chen, and Lena Miloslavsky

J. Appl. Phys. 107, 09A318 (2010); http://dx.doi.org/10.1063/1.3356231 (3 pages)

Online Publication Date: 20 April 2010

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Effect of reactive gas (oxygen/chlorine/fluorine) etching on NiFe magnetic properties was investigated. Experimental data showed 40% magnetic property degradation for F-containing gas etching, 10% degradation for O-containing gas etching, and 5% degradation for Cl-containing gas etching processes. X-ray diffraction analysis indicated that the crystallographic orientation remained the same upon the reactive gas etching, which is due to the low ion energy in plasma etching process as opposed to ion milling process with high input energy. It is proposed that the reported magnetic property degradation was mainly caused by the nonmagnetic dead layer formation, rather than the changes in the crystallographic orientation. The dead layer was determined by the NiFe thickness dependence of remnant magnetic flux variations between pre-etched and postetched samples. The dead layer remained nearly constant for O-containing gas etching process with increasing plasma processing time. The nonmagnetic dead layer of ∼ 40–50 Å formed in O-containing etching gas was observed in transmission electron microscopy cross-sectional image and was in very good agreement with the calculated value based on magnetic flux measurements. Combined magnetic and physical characterizations suggest that the dead layer thickness saturates at the initial stage of the plasma etching and magnetic property remained unchanged with increasing etching duration upon formation of the dead layer.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
75.50.Ss Magnetic recording materials
52.77.Bn Etching and cleaning
81.65.Cf Surface cleaning, etching, patterning
75.30.Cr Saturation moments and magnetic susceptibilities

Effects of B and Si contents on glass-forming ability and soft-magnetic properties in (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x glassy alloys

Huaijun Sun, Qikui Man, Yaqian Dong, Baolong Shen, Hisamichi Kimura, Akihiro Makino, and Akihisa Inoue

J. Appl. Phys. 107, 09A319 (2010); http://dx.doi.org/10.1063/1.3356233 (3 pages) | Cited 2 times

Online Publication Date: 20 April 2010

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The effects of B and Si contents on the glass-forming ability (GFA) and soft-magnetic properties of (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x (x = 22–30) alloys were investigated. The thermal stability of the supercooled liquid increased with increasing the B and Si contents from x = 24 to 28, and accompanying the decreases of liquidus temperature of alloys. As a result, The (Co0.89Fe0.057Nb0.053)100−x(B0.8Si0.2)x bulk glassy alloys with diameters up to 3.5 mm were synthesized in the composition range of x = 24–28. In addition to high GFA, the Co-based glassy alloys exhibit excellent soft-magnetic properties as well, i.e., moderate saturation magnetization of 0.51–0.72 T, low coercive force of 0.4–1.5 A/m, and high initial permeability of 22 340–29 570 at 1 kHz under a field of 1 A/m.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
64.70.P- Glass transitions of specific systems
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.50.Bb Fe and its alloys

Synthesis of submicron sized Fe20Ni80 particles and their magnetic properties

Daisuke Kodama, Kozo Shinoda, Ryo Kasuya, Kazuyuki Tohji, Masaaki Doi, and Jeyadevan Balachandran

J. Appl. Phys. 107, 09A320 (2010); http://dx.doi.org/10.1063/1.3334170 (3 pages) | Cited 2 times

Online Publication Date: 21 April 2010

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Fe–Ni alloy nanoparticles were synthesized by polyol process using hydrazine as a reduction assist reagent. Particle size, crystallite size, and crystal phases varied with the type of polyol. The saturation magnetizations of the as-synthesized Fe–Ni particles synthesized in ethylene glycol (EG) and 1-heptanol were similar to the bulk and were 73 emu/g and 83 emu/g, respectively. On the other hand, the coercivities of the same were 41 and 123 Oe. The coercivity of the Fe–Ni particles synthesized in EG decreased to 27 Oe after heat treatment. Though the magnetic properties were very similar irrespective of the polyol used in this study, the Mössbauer spectroscopic measurements revealed that Fe–Ni particles with single permalloy phase was synthesized only when EG was used.
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81.07.Bc Nanocrystalline materials
75.75.Jn Dynamics of magnetic nanoparticles
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Vv High coercivity materials
76.80.+y Mössbauer effect; other γ-ray spectroscopy

Effects of C addition in Fe65Co35 and Fe9.5Co90.5 soft magnetic films

V. Edon, S. Dubourg, J. Vernières, B. Warot-Fonrose, and J. F. Bobo

J. Appl. Phys. 107, 09A321 (2010); http://dx.doi.org/10.1063/1.3356232 (3 pages) | Cited 2 times

Online Publication Date: 21 April 2010

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Fe65Co35 and Fe9.5Co90.5 thin films with carbon addition were deposited by reactive sputtering and investigated in terms of static and dynamic magnetic properties. The acetylene rate was adjusted in order to deposit nanocrystalline soft magnetic films, with a high saturation magnetization, a high resistivity, and a low coercivity. The transition of the crystalline structure to a nanocrystalline or amorphous arrangement—giving rise to soft magnetic properties—depended on the Fe/Co ratio and the C content. The lowest coercivity of 0.4 Oe was obtained for a Fe9.5Co90.5 film with 0.95% of C2H2, whereas a Fe65Co35 film with 0.75% of C2H2 exhibited a coercivity of 0.7 Oe. The microwave properties of the Fe65Co35 layers remained stable over this C2H2 content whereas the resonance frequency of the Fe9.5Co90.5 films decreased with the C2H2/Ar ratio. A difference in the manner that the carbon was incorporated, depending on the Fe/Co ratio, may explain the observed magnetic properties.
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75.70.Ak Magnetic properties of monolayers and thin films
64.70.kd Metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
73.61.At Metal and metallic alloys

Demagnetizing factors for disk samples of nonideal soft magnetic materials

C. D. Graham and B. E. Lorenz

J. Appl. Phys. 107, 09A322 (2010); http://dx.doi.org/10.1063/1.3347916 (3 pages) | Cited 1 time

Online Publication Date: 22 April 2010

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To find out whether experimental magnetometric demagnetizing factors for disk samples of permalloy are valid for other magnetic materials with significant values of coercive field, we measured demagnetizing factors for disk samples of 1095 (high carbon) steel shim stock (Hc ≅ 45 Oe), and for cold-rolled pure nickel (Hc ≅ 23 Oe). The observed demagnetizing factors for steel agree well with those for permalloy but the values for cold-rolled nickel do not, at least for disk samples with diameter-to-thickness ratios d/t greater than 100. The criterion for agreement appears to be a hysteresis loop (M versus H) with straight, parallel sides up to at least half the saturation magnetization, implying a magnetization process controlled by the magnitude of the demagnetizing field.
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75.60.-d Domain effects, magnetization curves, and hysteresis
75.50.Vv High coercivity materials
75.78.-n Magnetization dynamics

Direct observation of an anisotropic in-plane residual stress induced by B addition as an origin of high magnetic anisotropy field of Ru/FeCoB film

Ken-ichiro Hirata, Shunsuke Gomi, Yasuhiro Mashiko, and Shigeki Nakagawa

J. Appl. Phys. 107, 09A323 (2010); http://dx.doi.org/10.1063/1.3350899 (3 pages) | Cited 1 time

Online Publication Date: 26 April 2010

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Although boron-free FeCo films prepared on a Ru underlayer exhibits isotropic in-plane magnetic property, boron added FeCoB films prepared on Ru underlayer revealed large in-plane magnetic anisotropy with a high anisotropy field of 500 Oe. The effect of boron addition on the in-plane anisotropic residual stress in FeCoB film was investigated using sin2 ψ method of x-ray diffraction analysis. Large isotropic compressive stress was observed in Ru/FeCo film. In contrast, anisotropic in-plane residual stress was observed in Ru/FeCoB film. The compressive stress along the easy axis of Ru/FeCoB film is released more than that along the hard axis. Such anisotropic residual stress is regarded as an origin of the in-plane magnetic anisotropy through inverse magnetostriction effect. Owing to the configuration of the facing targets sputtering system, boron atoms are sputtered and deposited anisotropically, and so they penetrate FeCo crystals and release the compressive stress along the incidence direction.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.15.Cd Deposition by sputtering
68.60.Bs Mechanical and acoustical properties
75.30.Gw Magnetic anisotropy

Magnetic anisotropy determination and magnetic hyperthermia properties of small Fe nanoparticles in the superparamagnetic regime

B. Mehdaoui, A. Meffre, L.-M. Lacroix, J. Carrey, S. Lachaize, M. Respaud, M. Gougeon, and B. Chaudret

J. Appl. Phys. 107, 09A324 (2010); http://dx.doi.org/10.1063/1.3348795 (3 pages) | Cited 5 times

Online Publication Date: 3 May 2010

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We report on the magnetic and hyperthermia properties of 5.5 nm in diameter iron nanoparticles synthesized by organometallic chemistry, which display the bulk magnetization. Quantitative analysis of alternative susceptibility measurements allows the determination of the effective anisotropy Keff = 1.3×105 J m−3. Hyperthermia measurements are performed at a magnetic field up to 66 mT and at frequencies in the range of 5–300 kHz. Maximum measured specific absorption rate (SAR) is 280 W/g. SAR displays a square dependence with the magnetic field below 30 mT but deviates from this power law at higher value. SAR is linear with the applied frequency for μ0H = 19 mT. These results are discussed in the light of linear response theory.
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87.85.Rs Nanotechnologies-applications
87.50.st Therapeutic applications
75.50.Tt Fine-particle systems; nanocrystalline materials
75.20.En Metals and alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Investigation of microstructure and soft magnetic properties of Fe65Co35 thin films deposited on different underlayers

Yanbo Li, Zhenghua Li, Xi Liu, Yu Fu, Fulin Wei, A. S. Kamzin, and Dan Wei

J. Appl. Phys. 107, 09A325 (2010); http://dx.doi.org/10.1063/1.3356228 (3 pages) | Cited 1 time

Online Publication Date: 4 May 2010

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Fe65Co35 /underlayer bilayer films were successfully prepared on different underlayer materials (Co93Fe7, Ni80Fe20, Cu, and Fe). The soft magnetic properties of Fe65Co35 films were improved when the texture changed from (110) to (200), which can be controlled by different underlayers. The conversion electron Mössbauer spectroscopy revealed that the angle between the effective magnetization and the normal direction of films with (110) texture is smaller than that with (200) texture. Calculations confirmed that the total anisotropy energy density of Fe65Co35 film with (110) texture is larger than that with (200) texture. Therefore, the soft magnetic properties of Fe65Co35 thin films with (200) texture are better than that with (110) texture.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.55.jm Texture
75.50.Ss Magnetic recording materials
76.80.+y Mössbauer effect; other γ-ray spectroscopy
68.55.-a Thin film structure and morphology
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