Materials Transactions Online

Materials Transactions, Vol.59 No.04 (2018) pp.585-589
© 2018 The Japan Institute of Metals and Materials

Tunnel-Type Magneto-Dielectric Effect and Its Annealing Study in Co-SiO2 Granular Films

Yang Cao1, Nobukiyo Kobayashi2, Shigehiro Ohnuma1, 2 and Hiroshi Masumoto1

1Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Sendai 980-8578, Japan
2Research Institute for Electromagnetic Materials, Sendai 982-0807, Japan

Tunnel-type magneto-dielectric (TMD) effect arising from the spin-dependent quantum tunneling between nano-sized granular pairs, has opened up new route for room temperature magnetoelectric fields. We first investigated the TMD properties in metal-oxide (Co-SiO2) granular films and their annealing effect in this work. Results show that the films exhibit a TMD ratio ($\Delta \varepsilon '/\varepsilon '_{0}$) of 1% with high electrical resistivity of >108 µΩ·m and intermediate optical transmittance in Co0.24-(SiO2)0.76 films. Annealing investigations suggest that the samples remain TMD response up to 573 K, and further increment in annealing temperature leads to the inter-diffusion between Co and SiO2 interfaces, thus producing the increasing oxidation of metallic Co. This study demonstrates the possibility of TMD effect in metal-oxide composite materials, and may be desirable for a variety of other wide oxide-based candidates for magnetoelectric device applications.


(Received 2017/12/14; Accepted 2018/01/30; Published 2018/03/25)

Keywords: granular nano-composites, magneto-dielectric properties, annealing effect

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