Magnetic domains and annealing-induced magnetic anisotropy in nanocrystalline soft magnetic materials

Suzuki, Kiyonori; Ito, Naoki; Saranu, S.; Herr, U.; Michels, Andreas; Garitaonandía, Jose Javier Saiz

doi:10.1063/1.2835068

Cited by 38 publications

(18 citation statements)

References 12 publications

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“…Therefore, another mechanism must be responsible for the increase of the coercivity. It was shown by Suzuki et al 20 that the effective anisotropy ͗K͘ in some nanocrystalline materials is given not only by the random local magnetocrystalline anisotropy K 1 ͓as given by Eq. ͑3͔͒, but induced anisotropy K u should also be taken into account:…”

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confidence: 99%

Nanocrystalline glass-coated FeNiMoB microwires

Komova

Varga

et al. 2008

Applied Physics Letters

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The evolution of the structure of glass-coated Fe 40 Ni 38 Mo 4 B 16 amorphous microwire with thermal treatments and its interplay with magnetism has been studied. As shown by x-ray diffraction, a primary crystallization process resulted into formation of ␥-͑Fe, Ni͒ nanocrystallites embedded in a residual amorphous matrix. The evolution of the saturation magnetization and the switching field after different thermal treatment was studied. Amorphous glass-coated microwires based on FeNi exhibit magnetic bistability even in the nanocrystalline state. This is explained by the high magnetoelastic anisotropy, which is also responsible for magnetic hardening after annealing at the temperatures above 670 K. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2969057͔Amorphous and nanocrystalline ferromagnetic microwires covered by a glass coating are very attractive material for applications, mainly as sensing elements in various sensors ͑i.e., magnetic field, coding, etc.͒, due to their outstanding magnetic characteristics, small dimensions and reliability on electrical, mechanical, and corrosive external effects ͑as a result of the Pyrex coating͒.1 These microwires, prepared by quenching and drawing technique, consist of a magnetic nucleus ͑with diameter from 1 -30 m͒ coated by a Pyrexlike glass ͑thickness of 2 -20 m͒. Due to their amorphous nature, magnetoelastic and shape anisotropy contributions govern their magnetic properties. As a result of abovementioned anisotropies, the domain structure of microwires with positive magnetostriction consists of single axial domain and their magnetization process is characteristic of the bistable behavior. 1,2The nanocrystalline microwires have been subject of different studies starting from Finemet based microwires, 3-7 as well as the Nanoperm based ones.8 Such nanocrystalline microwires are usually prepared by heat treatment. However, the microwires undergo strong stresses during the annealing due to the different thermal expansion coefficients of the metallic nucleus and the glass coating. As a result, a ␥-Fe phase appears in annealed glass-coated Finemet microwires instead of desired ␣-͑Fe, Si͒ phase.6,7 When the annealing is performed under high pressure, the formation of ␥-Fe phase is energetically more favorable due to its higher pack density, However, the ␥-Fe phase is nonmagnetic and deteriorates the good soft magnetic properties of nanocrystalline microwires. 6,7 It has been recently shown that partial crystallization of Fe 40 Ni 38 Mo 4 B 16 ribbon leads to the formation of nanocrystalline materials with ␥-͑Fe, Ni͒ nanocrystals having diameter of 10 nm.9 Annealing of such samples at T a = 700 K has been shown to be the optimum annealing temperature to obtain nanocrystalline Fe 40 Ni 38 Mo 4 B 16 alloy with optimized soft magnetic properties ͑lowest magnetostriction, lowest coercive field, and highest initial susceptibility͒. 10,11Since ␥-͑Fe, Ni͒ phase is ferromagnetic contrary to the paramagnetic ␥-Fe phase, it is a promising candidate for preparation of soft magne...

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Nanocrystalline glass-coated FeNiMoB microwires

Komova

Varga

et al. 2008

Applied Physics Letters

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“…3 K U due to induced magnetic anisotropies can dominate the effective magnetocrystalline anisotropy because of greater spatial coherency. [4][5][6] Toroidal tape wound cores of amorphous or nanocomposite ribbons can be annealed in a longitudinal or a transverse saturating field. Large K U is often undesirable for zero or longitudinally field annealed cores as it can dominate the effective magnetic anisotropy and result in large hysteretic losses due to domain wall pinning.…”

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Temperature stability of field induced anisotropy in soft ferromagnetic Fe,Co-based amorphous and nanocomposite ribbons

Ohodnicki

Laughlin

McHenry

et al. 2009

Journal of Applied Physics

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The temperature stability of field induced uniaxial anisotropy ͑K U ͒ was investigated by thermomagnetic treatments of ͑Co 1−x Fe x ͒ 89 Zr 7 B 4 amorphous ribbons after field annealing below and above the crystallization temperature. We conclude: ͑1͒ Field annealing treatments are necessary to properly investigate the temperature stability of K U , ͑2͒ K U of field crystallized alloys exhibit improved temperature stability relative to alloys remaining amorphous after field annealing, and ͑3͒ larger K U is obtained for field crystallization treatments as compared to zero-field crystallization followed by field reannealing. Field crystallization may be required for elevated temperature applications when field induced anisotropy is critical for performance.

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“…• C. Opposite situation is in the case of the critical field; it increases from room temperature (RT) up to Further macroscopic manifestation of the directional ordering is a linear shape of the hysteresis loop for material, after its annealing in a magnetic field, which is transversally oriented to the ribbon axis [9]. Hysteresis loop, measured on the Fe 43 Ni 43 Zr 7 Cu 1 B 6 alloy at RT, after its previous annealing for 1 h at T = 325…”

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Directional Ordering in Amorphous Fe₄₃Ni₄₃Zr₇Cu₁B₆Ferromagnetic Alloys

Varga

Vojtaník

et al. 2010

Acta Phys. Pol. A

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Development of the atomic directional ordering in the Fe43Ni43Zr7Cu1B6 alloy, during its conventional the same as after transverse magnetic field annealing, was experimentally studied by the amplitude dependence of susceptibility and hysteresis loops measurements, respectively. Diffusion processes of the mobile atoms caused perminvar effect, decrease of the initial susceptibility, increase of the critical field, and linear shape of the hysteresis loop. Uniaxial magnetic anisotropy, created during magnetic field annealing of the FeNiZrCuB alloy, was confirmed also by observation of the surface domain structure.

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Magnetic domains and annealing-induced magnetic anisotropy in nanocrystalline soft magnetic materials

Cited by 38 publications

References 12 publications

Nanocrystalline glass-coated FeNiMoB microwires

Nanocrystalline glass-coated FeNiMoB microwires

Temperature stability of field induced anisotropy in soft ferromagnetic Fe,Co-based amorphous and nanocomposite ribbons

Directional Ordering in Amorphous Fe₄₃Ni₄₃Zr₇Cu₁B₆Ferromagnetic Alloys

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Magnetic domains and annealing-induced magnetic anisotropy in nanocrystalline soft magnetic materials

Cited by 38 publications

References 12 publications

Nanocrystalline glass-coated FeNiMoB microwires

Nanocrystalline glass-coated FeNiMoB microwires

Temperature stability of field induced anisotropy in soft ferromagnetic Fe,Co-based amorphous and nanocomposite ribbons

Directional Ordering in Amorphous Fe43Ni43Zr7Cu1B6Ferromagnetic Alloys

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Directional Ordering in Amorphous Fe₄₃Ni₄₃Zr₇Cu₁B₆Ferromagnetic Alloys