Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Tunnel-Type Magneto-Dielectric Effect and Its Annealing Study in Co–SiO2 Granular Films
Yang CaoNobukiyo KobayashiShigehiro OhnumaHiroshi Masumoto
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2018 Volume 59 Issue 4 Pages 585-589


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 () 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.

Fig. 3 (a) Frequency dependence of the real part of dielectric constants for x = 0.24, with and without the application of magnetic field H = 800 kA/m; inset presents the detail of dielectric difference Δε' = ε'H - ε'0 between dielectric constants ε′ with and without magnetic field. (b) Frequency dependence of the magneto-dielectric response Δε'/ε'0 for various x values from 0.12 to 0.24; insets show the pictures of films deposited on quartz (SiO2) substrate, which may reflect their optical transmittance of 450-nm-thick films with different Co concentration from 0.12 to 0.27. Fullsize Image
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© 2018 The Japan Institute of Metals and Materials
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