Yu Hasegawa

Giant spin Hall effect in perpendicularly spin-polarized FePt/Au devices

Conversion of charge current into pure spin current and vice versa in non-magnetic semiconductors or metals, which are called the direct and inverse spin Hall effects (SHEs), provide a new functionality of materials for future spin-electronic architectures. Thus, the realization of a large SHE in a device with a simple and practical geometry is a crucial issue for its applications. Here, we present a multi-terminal device with a Au Hall cross and an FePt perpendicular spin injector to detect giant direct and inverse SHEs at room temperature. Perpendicularly magnetized FePt injects or detects perpendicularly polarized spin current without magnetic field, enabling the unambiguous identification of SHEs. The unprecedentedly large spin Hall resistance of up to 2.9 mOmega is attributed to the large spin Hall angle in Au through the skew scattering mechanism and the highly efficient spin injection due to the well-matched spin resistances of the chosen materials.

Optimization of a Switched Reluctance Motor Made of Permendur

A switched reluctance (SR) motor has a doubly salient pole structure. A stator has concentrated windings on each pole, while a rotor is only made of iron core. Therefore, the SR motor is expected as a low cost, extremely robust, variable speed motor. The performance of the SR motor greatly depends on magnetic properties of core material since it consists of only laminated-core and windings. This paper investigates the performance of an SR motor made of permendur which has extremely high saturation flux density and very low core loss. Motor torque, iron loss, and efficiency of the SR motor are estimated by finite element method (FEM). Furthermore, a suitable structure for the SR motor made of permendur is examined based on the design of experiments.

Characteristics of novel flux barrier type outer rotor IPM motor with rare-earth and ferrite magnets

This paper presents a novel flux barrier type outer rotor interior permanent magnet (IPM) motor which has both rare-earth and ferrite magnets. The proposed IPM motor has two air layers in the outer rotor. The rare-earth magnets are inserted into the first layer, while the ferrite magnets are placed into the second one. The torque performance of the proposed IPM motor is larger than that of the conventional one, although the amount of rare-earth magnet is almost half. The validity and availability of the proposed IPM motor are proved by experiment and a finite element method (FEM).

A Novel Switched Reluctance Motor With the Auxiliary Windings and Permanent Magnets

This paper presents a novel switched reluctance (SR) motor that has auxiliary windings and permanent magnets on the stator yoke. It can be driven by an asymmetric half-bridge converter in the same manner as the conventional SR motor, and the performance is improved by the auxiliary windings and magnets. The characteristics of the proposed SR motor are demonstrated by finite element method (FEM) and experiment. In addition, operating principle and characteristics in the case of generating mode are indicated.

Development of a Switched Reluctance Motor made of Permendur

A switched reluctance (SR) motor consists of stator and rotor cores, and windings. Both the stator and rotor have salient poles. The stator has concentrated windings on each salient pole. On the other hand, the rotor has no windings and no permanent magnets. Therefore, the SR motor is a low cost, extremely robust, and wide-range variable-speed motor. The performance of the SR motor greatly depends on magnetic properties of core material since it consists of only iron cores and windings. This paper presents the development of a novel SR motor made of permendur which has extremely high saturation flux density and very low core loss. Two types of SR motors, one is made of conventional non-oriented Si steel, the other is made of permendur, are compared by simulation and experiment. It is demonstrated that the torque of the SR motor made of permendur is greater than that of the conventional Si steel by 20%.

Experimental verification of performance of a switched reluctance motor made of permendur

This paper experimentally verifies the performance of a switched reluctance (SR) motor made of permendur. The permendur, which is an alloy created by mixing 49% cobalt with iron, has extremely high saturation flux density and very low core loss. Two types of 12/8-pole SR motors which have the same dimensions but different core material; one is conventional non-oriented Si steel and the other is permendur, are made on a trial basis to compare. As a result of experiment, the SR motor made of permendur demonstrates the better performance as compared to the conventional one in regard to torque, rotational speed, and efficiency characteristics.