Shunji Yanase

A large thermal elasticity of the ordered FeRh alloy film with sharp magnetic transition

Thermal elasticity and electrical resistivity with the magnetic phase transition were studied in FeRh alloy films prepared by ion-beam sputtering and subjected to post-annealing. Fe/sub 49.7/Rh/sub 50.3/ and Fe/sub 48.9/Rh/sub 51.1/ films deposited on conventional glass substrate and subjected to post-annealing at 600/spl deg/C for 90 min, respectively. Both films show a considerably sharp transition. In particular, Fe/sub 49.7/Rh/sub 50.3/ film exhibits small thermal hysteresis of about 20/spl deg/C width, which is only about 2 times over than that of bulk. Furthermore, a large abrupt thermal strain over 2/spl times/10/sup -3/ was observed with the magnetic transition. These results indicate that strictly controlled an equiatomic composition is an effective way to obtain the FeRh film with abrupt magnetic phase transition under low temperature and short time annealing.

AC magnetic properties of electrical steel core under DC-biased magnetization

Abstract AC magnetic properties of electrical steel core under DC-biased magnetization have been measured and discussed. The biased magnetization Δ B depends not only on DC-biased field H DC but also on AC magnetization B m and the magnetic losses increase with Δ B at the same B m . We discuss this loss increase from the viewpoint of frequency dependence of losses.

Magnetic properties of electrophoretic deposited ferrite particulate films

To fabricate ferrite films, electrophoretic deposition (EPD) of magnetite fine particles, synthesized by Fe/sup 2+//spl rarr/Fe/sup 3+/ oxidation, in water dispersion mixtures was carried out at room temperature. It is shown that densely packed ferrite films with a thickness of 9.2 /spl mu/m can be deposited via EPD from magnetite fine particles with a size of 10-30 nm onto a copper substrate. The film exhibited soft magnetic properties almost the same as raw magnetite particles.

Magnetic Property of Iron-Dust Cores With Mixture of Ferromagnetic Ferrite Powder and Alumina Powder

Iron-dust cores are produced from insulated iron particles by using the powder metallurgy pressure forming process. These dust cores are suitable for small motor cores because of their high shape flexibility; however, the iron loss of iron-dust cores is larger than conventional laminated cores. Generally, the insulation material between the iron particles degrades the magnetic property of the core. In this paper, the magnetic property of the iron-dust core in which the resin, which is usually used as insulation material, is replaced by the soft magnetic Mn-Zn ferrite or alumina is examined. We have found that the iron-dust core mixed with alumina particles shows higher space factor, 10% lower iron loss, and 30% higher permeability. Contrary to expectation, the magnetic properties of the iron-dust core deteriorate by mixing with soft magnetic Mn-Zn ferrite.

High Coercivity of Co-Ferrite Thin Films Prepared by Sol–Gel Method

Magnetic properties related to nano-structure have been investigated for sol-gel grown spinel Co-ferrite thin films of which thickness was 200-300 nm controlled by spin coating. The magnetic properties depended on the annealing temperature, and the coercivity of 6.3kOe was obtained at 923 K, which is about three times higher than that ever reported in Co-ferrite thin films by sol-gel method. The microstructure transformed into columnar from granular at the annealing temperature of 923 K, where magnetic anisotropy and high squareness ratio was observed

New Soft Magnetic Material Bonding Approach Using Ceramic Precursors and Ceramic Nanopowder

In this paper, we propose a new metal bonding method using a ceramic precursor (zirconium butoxide or titanium tetraisopropoxide) or a ceramic nano powder. Magnetic hysteresis curves of the bonded specimen did not change significantly after bonding in terms of the maximum magnetic field strength, the coercive force, and the residual magnetization. Iron loss of the specimen bonded using titanium tetraisopropoxide at 50 Hz increased by just 2.5%. The maximum shear strength per unit area was 0.29 N/mm2.

AC Magnetic Properties of Electrical Steel Sheet Under Two-Dimensional DC-Biased Magnetization

AC magnetic properties of electrical steel sheets are generally evaluated under symmetrical alternating magnetization in the standard magnetic measurement. However, magnetizing conditions of electrical steel sheets in electromagnetic machines are not always symmetric and alternating magnetization. This paper presents a new measuring system for AC magnetic properties of electrical steel sheets under two-dimensional DC-biased magnetization and discusses the properties under DC-biased magnetization.

Development of the apparatus for measuring magnetic properties of electrical steel sheets in arbitrary directions under compressive stress normal to their surface

In designing motors, one must grasp the magnetic properties of electrical steel sheets considering actual conditions in motors. Especially important is grasping the stress dependence of magnetic power loss. This paper describes a newly developed apparatus to measure two-dimensional (2-D) magnetic properties (properties under the arbitrary alternating and the rotating flux conditions) of electrical steel sheets under compressive stress normal to the sheet surface. The apparatus has a 2-D magnetic excitation circuit to generate magnetic fields in arbitrary directions in the evaluation area. It also has a pressing unit to apply compressive stress normal to the sheet surface. During measurement, it is important to apply uniform stress throughout the evaluation area. Therefore, we have developed a new flux density sensor using needle probe method. It is composed of thin copper foils sputtered on electrical steel sheets. By using this sensor, the stress can be applied to the surface of the specimen without influence of this sensor. This paper described the details of newly developed apparatus with this sensor, and measurement results of iron loss by using are shown.In designing motors, one must grasp the magnetic properties of electrical steel sheets considering actual conditions in motors. Especially important is grasping the stress dependence of magnetic power loss. This paper describes a newly developed apparatus to measure two-dimensional (2-D) magnetic properties (properties under the arbitrary alternating and the rotating flux conditions) of electrical steel sheets under compressive stress normal to the sheet surface. The apparatus has a 2-D magnetic excitation circuit to generate magnetic fields in arbitrary directions in the evaluation area. It also has a pressing unit to apply compressive stress normal to the sheet surface. During measurement, it is important to apply uniform stress throughout the evaluation area. Therefore, we have developed a new flux density sensor using needle probe method. It is composed of thin copper foils sputtered on electrical steel sheets. By using this sensor, the stress can be applied to the surface of the specimen without infl...

High Frequency Properties of Thick Ferrite Particulate Films Composed of Ultra Fine Particles

We have previously demonstrated a new fabrication technique, which is called electrophoretic deposition (EPD), to deposit ferrite particulate films at room temperature. EPD is a simple and low cost method for forming dense ceramic films from particulate precursors. Using this method, thick ferrite particulate films were formed rapidly (300 nm/min.) that exhibited soft magnetic properties. The frequency dependence of the complex magnetic permeability was then analysed.

Magnetic properties of FeRh alloy films prepared by ion-beam sputtering

Summary form only given. The interesting features of equiatomic FeRh alloy with a magnetic phase transition exhibited around room temperature are very useful for micro electrical mechanical system (MEMS) devices. A few studies have been made for the preparation of the ordered FeRh thin films, and they succeeded in the preparation of well-defined films. However, the FeRh films have not been employed in any engineering applications. This is simply because such a sharp transition can only be realized with special conditions: the films deposited on quartz substrates should be annealed in vacuum at 1200/spl deg/C, or a special substrate such as an MgO single crystal is required. The purpose of this study is the reduction of post annealing temperature to obtain the ordered structure and a relatively sharp magnetic transition on conventional glass or silicon wafer substrates, by using ion-beam sputtering.