Entity

Time filter

Source Type

Ōsaka, Japan

Sepehri-Amin H.,University of Tsukuba | Sepehri-Amin H.,Japan National Institute of Materials Science | Li W.F.,Japan National Institute of Materials Science | Ohkubo T.,Japan National Institute of Materials Science | And 5 more authors.
Acta Materialia | Year: 2010

Microstructural evolution of hydrogenation-disproportionation-desorption-recombination processed Nd12.5Fe72.8Co8.0B6.5Ga0.2 powder has been investigated in relation to coercivity development during the desorption recombination process. Coercivity increases when residual NdH2 is completely dehydrogenated and the decomposed Nd is segregated at the grain boundaries of the Nd2Fe14B phase. Three-dimensional atom probe (3DAP) analysis indicates the segregation of Ga at the grain boundary. The reason for the enhancement of the coercivity by the trace addition Ga is discussed based on the 3DAP results. © 2009 Acta Materialia Inc. Source


Jiang Y.,Beihang University | Fujita T.,Japan Science and Technology Agency | Fujita T.,University of Hyogo | Uehara M.,NEOMAX Co. | And 5 more authors.
Applied Physics Express | Year: 2011

The mechanical properties of low-stress cantilevered Nd2Fe14B/Ta multilayered microstructures are characterized. The cantilevered microstructures are fabricated using silicon molding technique and XeF2 gas-phase silicon etching process. The magnetic microcantilevers show relatively high quality factors varying from 75 to 135. The Young's modulus of the Nd2Fe14B/Ta multilayered film is evaluated by fitting the resonance response of the microcantilevers, which is smaller than those of bulk Nd2Fe14B magnets due to the texture effect. The good mechanical properties of the microcantilevers indicate that Nd2Fe14B/Ta multilayered films can be used as a structural material for microsystem applications. In addition, the electromagnetic driving of the Nd2Fe14B/Ta magnetic microcantilever is also demonstrated. © 2011 The Japan Society of Applied Physics. Source


Jiang Y.,Japan Science and Technology Agency | Masaoka S.,University of Hyogo | Uehara M.,NEOMAX Co. | Fujita T.,Japan Science and Technology Agency | And 4 more authors.
Journal of Micromechanics and Microengineering | Year: 2011

This paper describes the micro-patterning of thick NdFeB magnetic films using a high-power plasma etching method. The effects of RF bias power and gas composition on the selectivity and etching rate are experimentally studied. A maximum etching rate of 60 nm min-1 is achieved with an inductively coupled plasma power of 500 W and a RF bias power of 200 W. A maximum selectivity of 0.26 between hard baked AZP4903 photoresist and NdFeB magnetic films is achieved when volumetric Cl2 concentration is 2.5%. NdFeB micro-magnets as thick as 4.2 μm are achieved by using AZP4903 photoresist. Magnetic film as thick as 10 μm can be patterned by using SU-8 photoresist with a thickness of 100 μm as the mask. The magnetic property of patterned microstructures is characterized using a vibrating sample magnetometer and the magnetic field distribution is measured using a Hall effect sensor IC. The characterization results indicate that the patterned magnetic microstructures have a high magnetic remanance of 1.0 T, which is comparable to that of the non-patterned NdFeB films. © 2011 IOP Publishing Ltd. Source


Jiang Y.,Beihang University | Jiang Y.,Japan Science and Technology Agency | Masaoka S.,University of Hyogo | Fujita T.,Japan Science and Technology Agency | And 7 more authors.
Journal of Micromechanics and Microengineering | Year: 2011

This paper describes the fabrication of MEMS-based electromagnetic energy harvesters for scavenging energy from the ambient vibration. The novel energy harvester is fabricated by bonding a vibrator with embedded micro-magnets and a stator with integrated microcoils. The micro-magnets are formed by using sputtering deposition of NdFeB/Ta multilayered magnetic films with a thickness of 10 νm and silicon molding techniques. High-aspect-ratio silicon micro-springs are fabricated using deep reactive ion etching to achieve large vibration amplitude. The microcoils fabricated by electroplating processes are serially connected for multiplication of the output voltages from individual magnet-coil units. The energy harvester is successfully fabricated and wire-bonded for characterization. The maximum voltage output of the energy harvester at 115 Hz is approximately 2 mV, which corresponds to a power density of 1.2 nW cm-3. The performance of the energy harvester could be greatly improved by protecting the micro-magnets from oxidation and decreasing the spacing between the vibrator layer and the stator layer. © 2011 IOP Publishing Ltd. Source


Jiang Y.,Beihang University | Jiang Y.,Japan Science and Technology Agency | Fujita T.,Japan Science and Technology Agency | Fujita T.,University of Hyogo | And 7 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2011

The silicon molding technique is described for patterning of NdFeB/Ta multilayered magnetic films and NdFeB magnetic powder at the micron scale. Silicon trenches are seamlessly filled by 12-mm-thick NdFeB/Ta multilayered magnetic films with a magnetic retentivity of 1.3 T. The topography image and magnetic field distribution image are measured using an atomic force microscope and a magnetic force microscope, respectively. Using a silicon molding technique complemented by a lift-off process, NdFeB magnetic powder is utilized to fabricate magnetic microstructures. Silicon trenches as narrow as 20 mm are filled by a mixture of magnetic powder and wax powder. The B-H hysteresis loop of the patterned magnetic powder is characterized using a vibrating sample magnetometer, which shows a magnetic retentivity of approximately 0.37 T. © 2011 Elsevier B.V. Source

Discover hidden collaborations