Masanobu Hanazono

Giant magnetic moment and other magnetic properties of epitaxially grown Fe16N2 single-crystal films (invited)

Single‐crystal Fe16N2 films have been grown epitaxially on Fe(001)/InGaAs(001) and InGaAs(001) substrates by molecular beam epitaxy (MBE). Saturation flux density Bs of Fe16N2 films has been demonstrated to be 2.8–3.0 T at room temperature, which is very close to the value obtained by Kim and Takahashi using polycrystalline evaporated Fe–N films. Temperature dependence of Bs has been measured. Bs changed with temperature reversibly up to 400 °C, while beyond 400 °C, Bs decreased irreversibly. X‐ray diffraction showed that Fe16N2 crystal is stable up to 400 °C, while beyond 400 °C, Fe16N2 dissolves into Fe and Fe4N, and also some chemical reactions between Fe16N2 and the substrate occurs. This caused the temperature dependence of Bs mentioned above. From the temperature dependence of Bs up to 400 °C, the Curie temperature of Fe16N2 is estimated to be around 540 °C by using the Langevin function. The above mentioned Bs of 2.9 T at room temperature and 3.2 T at −268 °C corresponded to an average magnetic mom...

Current-Voltage Characteristics of YBa2Cu3Oy/La0.7Ca0.3MnOz/YBa2Cu3Oy Trilayered-Type Junctions

YBa2Cu3Oy(superconductor)/La0.7Ca0.3MnOz(magnetic material)/YBa2Cu3Oy(superconductor) trilayered-type junctions were prepared on MgO(100) single-crystal substrates, and the current-voltage characteristics were examined. The top and bottom YBa2Cu3Oy layers were 200 nm thick, and the La0.7Ca0.3MnOz layer was 20, 30, 50 or 100 nm thick. A supercurrent was observed through all the La0.7Ca0.3MnOz layers, even the thickest one. Further investigation showed that a supercurrent could he observed through the 500-nm barrier layer.

Design and fabrication of thin‐film heads based on a dry process (invited)

High performance thin‐film heads for disk drive systems have been developed based on a dry process. Heads were computer simulated and optimal design was carried out. Relationships among Ni‐Fe composition, domain structure and wiggle of the read‐write waveform were obtained. Based on these results, optimum Ni‐Fe composition range was determined. A planarization procedure for an inbedding insulator of the conductor coil was developed. Also narrow track patterning and gap depth controlling procedures were developed. Using these procedures, a two‐layered seventeen‐turn thin‐film head for a large capacity disk drive system (23 Mb/in.2) has been developed. The head exhibited excellent read‐write characteristics.

Structures and magnetic properties of Fe/Cu multilayered films fabricated by a magnetron sputtering method

Fe and Cu single‐layered films and Fe/Cu multilayered films were prepared by an rf‐magnetron sputtering method, and the film structures and magnetic properties were investigated. Fe and Cu single‐layered films become continuous when their thickness is more than 4 nm for Fe and 10 nm for Cu. The crystal structure of Fe/Cu multilayered films depends on the thickness or continuity of Fe and Cu layers. A Fe 1.6 nm/Cu 2 nm multilayered film has a periodic structure. As the thickness of the Fe layer decreases, the magnetic flux density and coercivity decrease and the magnetostriction constant changes from negative to positive. Uniaxial magnetic anisotropy in the plane of the multilayered Fe/Cu films is observed when the Fe layer is discontinuous, but it is not clearly observed for a continuous Fe film.

Oxygen in SrS Phosphor Powder and Its Effects on Performance of Thin Film Electroluminescent Devices

This paper reports on oxygen and oxidation effects in SrS powder that were investigated in order to improve luminance of SrS-based thin-film electroluminescent devices, XPS analysis revealed that the SrS powder surface was oxidized by the adsorption of water, giving the surface products SrSO{sub 3} and free S. Adsorption of water on the surface proceeded rapidly when exposed to a moist atmosphere, and oxidation of the surface occurred when heated in a nitrogen atmosphere as well as in a vacuum. Higher luminance and a better build-up characteristic in the luminance-voltage curve of the EL cells were obtained through heat-treatment of evaporation sources in an H{sub 2}S atmosphere.

Fabrication of a thin film head using polyimide resin and sputtered Ni‐Fe films

Sputter‐deposited Ni‐Fe films and planarized polyimide resin (PIQ) were used for fabrication of an eight‐turn thin film head. Properties of the head were tested using a disk storage system.

TiO2 / SiO2 Multilayer Insulating Films for ELDs

Dielectric properties and the optical energy gap of TiO 2 /SiO 2 multilayer films prepared by sputtering were measured. The thickness ratio, TiO 2 /SiO 2 , was fixed at 1/3, and TiO 2 monolayer thickness, dt, was varied from 0.3 to 60 nm. The peak of the maximum charge density, which is the product of the dielectric constant and the breakdown field strength, was observed at dt=1 nm. The optical energy gap was constant for dt>2 nm, and increased as dt dropped below 2 nm

Temperature Dependence in Emission Characteristics of an Organic EL Cell with 8‐hydroxyquinoline Aluminum Emitting Layer

Current density-voltage characteristics, luminance, and emission spectra of an organic electroluminescent (EL) cell were measured at temperatures between -160 and 20 o C. An aromatic diamine and 8-hydroxyquinoline aluminum (Alq 3 ) were used as the hole transport and the emitting layers, respectively. The EL luminance at a constant current density of 1 mA/cm 2 was found to decrease with increasing temperature, and the photoluminescence intensity of the Alq 3 powder was also found to show a similar temperature dependence

Novel proximity effect between high-Tc superconductor and magnetic manganese oxide

Abstract A novel proximity effect between high-Tc superconductor and magnetic manganese oxide has been found. Supercurrents were observed through La0.7Ca0.3MnOz (LCMO) magnetic barrier as thick as 500 nm in YBCO/LCMO/YBCO trilayered junctions. We confirmed this proximity effect in coplanar-type junctions with spacing of 200 nm, and presented a possibility that this phenomenon occurs between NbN and LCMO. Furthermore we investigated current-voltage (I–V) characteristics and magnetic properties for Y1Ba2Cu3Oy/La1−xSrxMnOz(200nm)/Y1Ba2Cu3Oy (YBCO/LSMO/YBCO) junctions. I–V characteristics changed systematically with varying the magnetism of the barrier. When x value was 0.2, super-currents passed through the barrier, and it was found that ferromagnetism (Ms= 135 emu/cc) and supercurrents coexist in this proximity state. Magnetism of the LSMO is understood as a complicated and fluctuated state of ferromagnetic coupling in ab plane and antiferromagnetic coupling along c-axis. Considering supercurrents passed through the La1−xSrx(Mn3+1−xMn4+x)Oz along c-axis, our results suggest a novel proximity effect mechanism, that is antiferromagnetic spin fluctuation and charge fluctuation can transport Cooper-pairs over a long range.

Effects of Substrate Temperature during Phosphor Layer Deposition on Luminance of SrS:Ce Blue-Green-Emitting Thin-Film Electroluminescent Devices

In order to improve the luminance of blue-green-emitting SrS:Ce thin-film electroluminescent devices, the effects of substrate temperature (350-550°C) during phosphor layer deposition were studied. Two deposition procedures were used: sulfur coevaporation and sulfurization of evaporation sources. The luminance increased with increasing substrate temperature in both cases. As the substrate temperature increased, oxygen content decreased and sulfur content remained almost constant for coevaporation; however, sulfur content increased while oxygen content remained low when the sulfurization technique was used. These changes led to improvement in the crystallinity of the phosphor layers. Also, sulfur and oxygen contents in phosphor layers deposited at 550°C by both procedures were almost the same, and as a result, the luminance levels were almost the same.