https://www.jstage.jst.go.jp/article/matertrans1989/31/8/31_8_743/_pdf

High Saturation Magnetization and Soft Magnetic Properties of bcc Fe–Zr–B Alloys with Ultrafine Grain Structure

High Saturation Magnetization and Soft Magnetic Properties of bcc Fe–Zr–B and Fe–Zr–B–M (M=Transition Metal) Alloys with Nanoscale Grain Size

This paper reviews the current state of power supply technology platforms and highlights future trends and challenges toward realizing fully monolithic power converters. This paper presents a detailed survey of relevant power converter technologies, namely power supply in package and power supply on chip (PwrSoC). The performance of different power converter solutions reported in the literature is benchmarked against existing commercial products. This paper presents a detailed review of integrated magnetics technologies, primarily microinductors, a key component in realizing a monolithic power converter. A detailed review and comparison of different microinductor structures and the magnetic materials used as inductor cores is presented. The deposition techniques for integrating the magnetic materials in the microinductor structures are discussed. This paper proposes the use of two performance metrics or figures of merit in order to compare the dc and ac performance of individual microinductor structures. Finally, the authors discuss future trends, key challenges, and potential solutions in the realization of the “holy grail” of monolithically integrated power supplies (PwrSoC).

Review of Integrated Magnetics for Power Supply on Chip (PwrSoC)

This paper reviews our results on the development of a new type of soft magnetic material with high saturation magnetic flux density (B s ) combined with excellent soft magnetic properties. A mostly single bcc structure composed of bcc grains with about 10-20 nm in size surrounded by a small amount of intergranular amorphous layers was obtained by crystallization of amorphous phases prepared by melt-spinning and sputtering technique in Fe-rich regions of Fe-M-B (M=Zr, Nb, Hf) ternary systems. The typical nanocrystalline bcc Fe 90 Zr 7 B 3 , Fe 89 Hf 7 B 4 and Fe 84 Nb 7 B 9 alloys subjected to the optimum annealing exhibit high B s above 1.5 T as well as high effective permeability (μ e ) at 1 kHz above 20000. The high B s for the Fe-M-B alloys is resulting from the high Fe concentrations owing to high glass-forming ability of M(Zr, Hf, Nb) and B. The origin of the good soft magnetic properties for the alloys are listed as follows. (1) The apparent anisotropy is decreased by the combined effects of the formation of the nanoscale bcc structure and the achievement of rather strong magnetic coupling between the bcc grains through the intergranular ferromagnetic amorphous phase. (2) The small saturation magnetostriction (λ s ) results from the nonequilibrium bcc phase. The solute-rich inter-glanular amorphous phase with high Curie temperature (T c ) and high thermal stability has an important role in the achievement of the good soft magnetic properties through the formation of the nanoscale bcc structure and the attainment of the rather strong magnetic coupling between the bcc grains. The soft magnetic properties of the nanocrystalline Fe-M-B alloys were improved through the decrease in the bcc grain size and the increase in T c of the intergranular amorphous phase by optimizing heating rate in the crystallization process and adding small amounts of elements. For example, the improved Fe 84 Zr 3.5 Nb 3.5 N 8 Cu 1 alloy shows the high μ e of 100000 combined with the high B s of 1.53 T. This excellent μ e is comparable to those of nanocrystalline Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1 and the zero-magnetostrictive Co based amorphous alloys, and the high B s is comparable to those of the Fe based amorphous alloys with good soft magnetic properties. The Fe-M-B based alloys also have very low core losses, the sufficient thermal stability and the low stress-sensibility of the soft magnetic properties. Therefore, the nanocrystalline Fe-M-B alloys are expected as practical magnetic materials for magnetic transformers, inductors, and other devices and parts.

Nanocrystalline Soft Magnetic Fe–M–B (M=Zr, Hf, Nb) Alloys Produced by Crystallization of Amorphous Phase (Overview)

Magnetic amorphous alloys obtained by rapid quenching of the melt are excellent soft magnetic materials with a wide range of technological applications. They also represent a significant challenge to the scientific understanding of magnetic materials, since most of the existing theories of solids assume lattice periodicity. For these reasons, the magnetic and other properties of amorphous alloys have been very actively studied over the last decade. In recent years increasing attention has been directed to the fundamental understanding of the structural, thermal and magnetic properties of the amorphous alloys. It is not only scientifically but also technologically important to achieve such an understanding, since the amorphous alloys are, in many respects, so different from conventional crystalline magnetic materials. The author attempts to summarise recent progress in research on magnetic amorphous alloys and critically assesses the present level of understanding of this new class of magnetic materials, focusing mostly on the transition-metal-metalloid glasses. He starts with a review of early developments and a discussion on the nature of glasses and glass formation and proceeds to an extensive discussion of their atomic structure, both from the experimental and theoretical points of view.

https://iopscience.iop.org/article/10.1088/0034-4885/47/12/002/pdf

Magnetic amorphous alloys: physics and technological applications

A study was made of the properties and structure of Co-Zr-O nano-granular films prepared by rf reactive sputtering in an atmosphere of argon and oxygen gases. We found soft magnetic Co-Zr-O films in a wide compositional range near Co-ZrO/sub 2/ and investigated systematically the compositional dependence of their magnetic properties and electrical resistivity. The films near Co/sub 60/Zr/sub 10/O/sub 30/ simultaneously have anisotropy fields more than 150 Oe, coercivities less than 3 Oe, saturation magnetizations more than 9 kG, and electrical resistivities more than 1000 /spl mu//spl Omega/cm. The frequency response of permeability of these films is excellent. And they show a high resonance frequency exceeding 3 GHz.

Co-Zr-O nano-granular thin films with improved high frequency soft magnetic properties

Noise suppression in downsized circuits utilizing magnetic granular films is demonstrated. Films of Fe-Al-O with thickness of 2 /spl mu/m which exhibit very high /spl mu/" dispersion in the quasimicrowave band were found to work as noise suppressors. The films were attached onto a micro-strip line and the transmission characteristics were compared. This work is the first to verify that films with only 2 /spl mu/m thickness can play a role in suppression of high frequency conduction noise in the quasimicrowave band. The results suggest a possibility of thin film noise suppressors which can be integrated into micron scale semiconductor circuits.

High-frequency noise suppression in downsized circuits using magnetic granular films

A detailed investigation on the thermal expansion, magnetic properties and electrical resistance of rapidly quenched amorphous (Fe,Co,Ni)-Zr alloys has been undertaken. Magnetic properties of these alloys are reported separately in this conference. The thermal expansion curves exhibit typical invar characteristics below the Curie temperature due to positive spontaneous volume magnetostriction us similar to those for Fe-Ni crystalline invar alloys. The reduced magnetization decreases strongly with increasing temperature being analogous to the case of other amorphous invar alloys. Moreover, w s at 0 K and electrical resistance at room temperature and Liq. N 2 temperature increase in the invar region. Amorphous ternary alloys of (Fe,Co, Ni) 90 Zr 10 with about 72 at% Fe have the invar characteristics in a wide temperature range and in this composition range, the volume magnetostriction and electrical resistance show maximum values of about 1.5 × 10-2and 160 μΩcm respectively.

Invar characteristics of amorphous (Fe,Co and Ni)-Zr alloys

Soft-magnetic thin films with high magnetic flux densities of about 23 kG have been fabricated in the (Fe–Co)–Zr–O nanogranular system The films were prepared by reactive sputtering under an oxygen–argon atmosphere using a target of Fe–Co–Zr alloys The microstructure was composed of base-centered-cubic Fe–Co nanograins, where nanoparticles of amorphous Zr oxide are dispersed These Zr-oxide nanoparticles are thought to hinder the growth of Fe–Co grains during the film deposition, causing low coercivity

FeCo–Zr–O nanogranular soft-magnetic thin films with a high magnetic flux density

Magnetic properties of melt-quenched amorphous ribbons having the general composition TM 100-x Zr x (TM= Fe,Co and/or Ni) have been investigated. Composition dependence of Curie temperature, Tc and magnetic moment, n B in Co 100-x Zr x and Ni 100-x Zr x alloys is similar to Co- and Ni-metalloid amorphous alloys. However, the decrement of Zr content in the Fe 100-x Zr x alloys causes both Tc and n B to decrease, and n B extrapolates at x=0 to almost 0 μ B . Such an unusual behavior of Tc and n B is also found on the Fe-rich portion of (Fe-Co-Ni) 90 - Zr 10 ternary system and Tc and n B of the Fe 90 Zr 10 alloy are 243 K and 1.29 μ B /Fe atom, respectively. For the Co 90 Zr 10 alloy the value of longitudinal linear magnetostriction λ is +3 × 10-6, and the zero-magnetostrictive composition lies near (Co .88 Ni .12 ) 90 Zr 10 and shifts to Fe-rich side with increasing Ni content.

Shigehiro Ohnuma

Papers

Co-Zr-O nano-granular thin films with improved high frequency soft magnetic properties

High-frequency noise suppression in downsized circuits using magnetic granular films

Invar characteristics of amorphous (Fe,Co and Ni)-Zr alloys

FeCo–Zr–O nanogranular soft-magnetic thin films with a high magnetic flux density

Magnetic properties of (Fe, Co and Ni) - Zr amorphous alloys