Journal of the Magnetics Society of Japan
Online ISSN : 1882-2932
Print ISSN : 1882-2924
ISSN-L : 1882-2924
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Thin Films, Fine Particles, Multilayers, Superlattices
  • Y. Nakamura, M. Ohtake, T. Kawai, M. Futamoto, F. Kirino, N. Inaba
    2021 Volume 45 Issue 6 Pages 136-141
    Published: November 01, 2021
    Released: November 01, 2021
    [Advance publication] Released: September 30, 2021
    JOURNAL OPEN ACCESS

      (Fe0.7Co0.3)100–xBx (x = 0–15, at. %) alloy films of 100 nm thickness are prepared on VN(001) single-crystalline underlayers at 600 °C and on VN poly-crystalline underlayers at room temperature (RT). A high substrate temperature of 600 °C is used to promote epitaxial film growth on VN(001) underlayer. Influences of B content on the structural, magnetic, and magnetostrictive properties are investigated. The films formed on VN(001) underlayers involve bcc(001) epitaxial crystalline phase, whereas those formed on VN poly-crystalline underlayers consist of poly-crystalline and/or amorphous phases. Surface roughness of film formed on VN(001) underlayer at 600 °C increases with increasing the B content, whereas flat surfaces are realized for the films formed on VN poly-crystalline underlayers at RT. The surface morphology is influenced by both the substrate temperature and the B content. The films with flat surfaces show good soft magnetic properties. In contrast, rough surface causes an increase in the saturation magnetic field. In the case of films formed on VN(001) single-crystalline underlayer at 600 °C, magnetostriction value of λ100 increases from +200 × 10–6 to +310 × 10–6, as the B content increases from x = 0 to 5. With further increasing the B content, λ100 value decreases due to unsaturation of magnetization at a magnetic field of 1200 Oe which is the maximum value used for measurement. λ111 values are nearly zero (–10 × 10–6 – +20 × 10–6) for all the investigated B contents. Slight addition of B atoms around 5 at. % is effective in enhancing the λ100 value, while keeping high crystallographic quality, flat surface, and soft magnetic property. On the contrary, the films formed on VN poly-crystalline underlayers at RT show moderately large λ values of about +60 × 10–6 for all the B contents. The present study shows that control of B content and realization of flat surface are important factors in enhancing the magnetostriction of Fe-Co-B film.

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  • N. Ota, A. Li, L. Nemes, M. Otsuka
    2021 Volume 45 Issue 6 Pages 142-148
    Published: November 01, 2021
    Released: November 01, 2021
    JOURNAL OPEN ACCESS

      Fullerene C60 shows astronomical four infrared bands (IR) of carbon rich planetary nebulae. However, there remain many unidentified bands. Our previous paper revealed that single void-defect induced graphene molecule reproduce many astronomical bands. In this paper, we investigated a series of multiple-void induced graphene molecules. We tried spin dependent DFT calculation. Model molecules are C23 (one carbon pentagon ring among hexagon network), C22 (two), and C21 (three). Those were all magnetic molecules with spin state of Sz =2/2, 2/2 and 4/2 respectively. Calculated IR was compared with astronomical observation. The largest astronomical band at 18.9 micrometer was found in C23. Second largest band at 17.4 micrometer appeared both in C22 and C21. Other major bands from 6 to 10 micrometer were reproduced well by a combination of C23, C22 and C21. Similarly, larger size graphene molecules of C53, C52 and C51 were also magnetic and reproduced astronomical bands as well. Weighting sum IR of those molecules could successfully trace astronomical 12 bands from 6 to 20 micrometer. A series of multiple void induced graphene would be major component of astronomical carbon. Fullerene C60 would be one of them.

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