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0966-T03-02

Capacitance Tunability of Magneto-electric Material:Cr2O3 using Ferromagnetic (La,Sr)MnO3 Electrode Takeshi Yokota, Takaaki Kuribayashi, Takeshi Shundo, Keita Hattori, Yasutoshi Sakakibara, and Manabu Gomi Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 4668555, Japan

ABSTRACT We have investigated the dielectric properties of Cr2O3 films using (La0.66, Sr0.33)MnO3 as a ferromagnetic electrode. The relationship between those properties and the film’s crystallinity was also investigated. The well crystallized sample exhibited a low leakage current density. Although all samples showed capacitance decrease with an increase in applied voltage, the decrease ratio was the largest for the sample with the lowest leakage current density. Since an identical Cr2O3 film using a non-magnetic electrode showed no capacitance changes with the applied voltage, it was suggested that the dielectric properties of the Cr2O3 film were affected by the ferromagnetic film. INTRODUCTION Magneto-electronics using magneto-electric (ME) effects such as those produced by multi-ferroic materials has received attention because magnetic or ferroelectric properties can be controlled by an external electric or magnetic field. [1-2] We have focused on the dielectric properties of Cr2O3 thin film as a ME material. Although Cr2O3 shows ME behavior, the induced magnetic moment is quite small even with an electric field of 106 V/cm for ME devices. [3-6] However, if we apply an electric field up to about 108 V/cm on the thin film, the induced magnetic moment is high enough to affect the magnetic properties such as the ferromagnetic/Cr2O3 hetero interface. [7] Moreover, the induced magnetic moment will affect the dielectric properties themselves. For example, in the case of the multi-ferroic material BiFeO3, in order to achieve ferromagnetic properties, an oxygen deficiency must be introduced to enhance the super exchange coupling of Fe-O-Fe. [8-9] This means that ferroelectric properties should become worse as the leakage current density increases. In the case of Cr2O3, it is not necessary to introduce an oxygen deficiency to obtain the magnetic feature; nevertheless, it is important to know the influence of an external electric field, magnetic field or magnetic interaction on the dielectric properties. Hence, in this paper we investigated the dielectric properties of Cr2O3 thin film using a ferromagnetic (La0.66, Sr0.33)MnO3 (LSMO) electrode.

EXPERIMENT Cr2O3 thin films were prepared on epitaxially grown LSMO film on a SrTiO3 (100) substrate using the radio-frequency (RF) magnetron sputtering method. The La and Sr composition of the LSMO film used were 0.66 and 0.33, respectively, because this ratio shows the highest Curie temperature. The base pressure before introducing the sputtering gas was 3.0 ×10-4 Pa and the gas pressure during deposition was 8.0 ×10-1 Pa. The gas was a mixture of Ar and O2, and the ratio was fixed at 16: 1. The growth temperature was set at either 200, 300 or 400 °C. The