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Electrical control of the ferromagnetic phase transition in cobalt at room temperature

Abstract

Electrical control of magnetic properties is crucial for device applicationsin the field of spintronics1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20. Although the magnetic coercivity or anisotropy has been successfully controlled electrically in metals 9,15,17 as well as in semiconductors6,10,11,13, the electrical control of Curie temperature has been realized only in semiconductors at low temperature4,5,8. Here, we demonstrate the room-temperature electrical control of the ferromagnetic phase transition in cobalt, one of the most representative transition-metal ferromagnets. Solid-state field effect devices consisting of a ultrathin cobalt film21,22 covered by a dielectric layer and a gate electrode were fabricated. We prove that the Curie temperature of cobalt can be changed by up to 12 K by applying a gate electric field of about ±2 MV cm−1. The two-dimensionality of the cobalt film may be relevant to our observations. The demonstrated electric field effect in the ferromagnetic metal at room temperature is a significant step towards realizing future low-power magnetic applications.

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Figure 1: Switching of ferromagnetism by electric field at room temperature and measurement configuration.
Figure 2: Magnetization curves under gate voltages obtained by using the anomalous Hall effect.
Figure 3: Arrott plots.
Figure 4: Temperature dependences of spontaneous Hall resistance under gate voltages and Curie temperatures as a function of gate voltage.

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Acknowledgements

We thank O. Sakae and S. Meguro from NEOARK Corporation for their technical help in the magneto-optical Kerr effect measurement. This work was partly supported by the PRESTO program from JST, Grant-in-Aid for Young Scientists (A) from MEXT, Grant-in-Aid for Scientific Research (S) from JSPS, and research grants from the Murata Science Foundation and the Yazaki Memorial Foundation.

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D.C. and T.O. planned and supervised the study. S.F. and N.I. provided the films. D.C. fabricated the devices. D.C. and K.S. collected and analysed the data. D.C. wrote the manuscript with input from K.K. and T.O. All authors discussed the results.

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Correspondence to D. Chiba.

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The authors declare no competing financial interests.

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Chiba, D., Fukami, S., Shimamura, K. et al. Electrical control of the ferromagnetic phase transition in cobalt at room temperature. Nature Mater 10, 853–856 (2011). https://doi.org/10.1038/nmat3130

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