Tunable frequency response of tunnel-type magneto-dielectric effect in Co-MgF2 granular films with different content of Co

Y. Cao; A. Umetsu; N. Kobayashi; S. Ohnuma; H. Masumoto

doi:10.1063/1.4985335

Tunable frequency response of tunnel-type magneto-dielectric effect in Co-MgF₂ granular films with different content of Co

Y. Cao, A. Umetsu, N. Kobayashi, S. Ohnuma, H. Masumoto

Research output: Contribution to journal › Article › peer-review

17 Citations (Scopus)

Abstract

We have demonstrated the frequency dependence of the tunnel-type magneto-dielectric (TMD) effect in superparamagnetic Co_x-(MgF₂)_1-x granular nanostructures by precise variations of x from 0.06 to 0.2. The structures consist of the nanometer-sized Co granules embedded in a crystallized MgF₂ dielectric matrix. We observed an increased peak dielectric change Δϵ′/ϵ′₀ from 0.8% to 3% at a specific frequency f_TMD, and tunable f_TMD was achieved from 8 kHz to 6.6 MHz by increasing x. Theoretical fittings predict that the narrow distribution of relaxation time gave rise to an enhanced Δϵ′/ϵ′₀ and the narrowing of f_TMD; the position variation of f_TMD was attributed to the change in the intergranular distance between a pair of two neighboring granules. This study may help understand the fundamental physics between the TMD effect and nanometric structure and indicate that the films may work at higher frequency for devices with tunable dielectrics.

Original language	English
Article number	122901
Journal	Applied Physics Letters
Volume	111
Issue number	12
DOIs	https://doi.org/10.1063/1.4985335
Publication status	Published - 2017 Sept 18

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title = "Tunable frequency response of tunnel-type magneto-dielectric effect in Co-MgF2 granular films with different content of Co",

abstract = "We have demonstrated the frequency dependence of the tunnel-type magneto-dielectric (TMD) effect in superparamagnetic Cox-(MgF2)1-x granular nanostructures by precise variations of x from 0.06 to 0.2. The structures consist of the nanometer-sized Co granules embedded in a crystallized MgF2 dielectric matrix. We observed an increased peak dielectric change Δϵ′/ϵ′0 from 0.8% to 3% at a specific frequency fTMD, and tunable fTMD was achieved from 8 kHz to 6.6 MHz by increasing x. Theoretical fittings predict that the narrow distribution of relaxation time gave rise to an enhanced Δϵ′/ϵ′0 and the narrowing of fTMD; the position variation of fTMD was attributed to the change in the intergranular distance between a pair of two neighboring granules. This study may help understand the fundamental physics between the TMD effect and nanometric structure and indicate that the films may work at higher frequency for devices with tunable dielectrics.",

author = "Y. Cao and A. Umetsu and N. Kobayashi and S. Ohnuma and H. Masumoto",

note = "Funding Information: This work was funded by the Japan Society for the Promotion of Science (JSPS) KAKENHI under Grant-in-aid Nos. 17H03385 and 15J03637. Dr. T. Miyazaki is greatly acknowledged for the TEM observation. Publisher Copyright: {\textcopyright} 2017 Author(s).",

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doi = "10.1063/1.4985335",

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AU - Cao, Y.

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AU - Ohnuma, S.

AU - Masumoto, H.

N1 - Funding Information: This work was funded by the Japan Society for the Promotion of Science (JSPS) KAKENHI under Grant-in-aid Nos. 17H03385 and 15J03637. Dr. T. Miyazaki is greatly acknowledged for the TEM observation. Publisher Copyright: © 2017 Author(s).

PY - 2017/9/18

Y1 - 2017/9/18

N2 - We have demonstrated the frequency dependence of the tunnel-type magneto-dielectric (TMD) effect in superparamagnetic Cox-(MgF2)1-x granular nanostructures by precise variations of x from 0.06 to 0.2. The structures consist of the nanometer-sized Co granules embedded in a crystallized MgF2 dielectric matrix. We observed an increased peak dielectric change Δϵ′/ϵ′0 from 0.8% to 3% at a specific frequency fTMD, and tunable fTMD was achieved from 8 kHz to 6.6 MHz by increasing x. Theoretical fittings predict that the narrow distribution of relaxation time gave rise to an enhanced Δϵ′/ϵ′0 and the narrowing of fTMD; the position variation of fTMD was attributed to the change in the intergranular distance between a pair of two neighboring granules. This study may help understand the fundamental physics between the TMD effect and nanometric structure and indicate that the films may work at higher frequency for devices with tunable dielectrics.

AB - We have demonstrated the frequency dependence of the tunnel-type magneto-dielectric (TMD) effect in superparamagnetic Cox-(MgF2)1-x granular nanostructures by precise variations of x from 0.06 to 0.2. The structures consist of the nanometer-sized Co granules embedded in a crystallized MgF2 dielectric matrix. We observed an increased peak dielectric change Δϵ′/ϵ′0 from 0.8% to 3% at a specific frequency fTMD, and tunable fTMD was achieved from 8 kHz to 6.6 MHz by increasing x. Theoretical fittings predict that the narrow distribution of relaxation time gave rise to an enhanced Δϵ′/ϵ′0 and the narrowing of fTMD; the position variation of fTMD was attributed to the change in the intergranular distance between a pair of two neighboring granules. This study may help understand the fundamental physics between the TMD effect and nanometric structure and indicate that the films may work at higher frequency for devices with tunable dielectrics.

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Tunable frequency response of tunnel-type magneto-dielectric effect in Co-MgF₂ granular films with different content of Co

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