17:45 〜 18:00
▲ [24p-E202-15] Modulation of dielectric constant and VCMA efficiency in FeB/MgO/HfO2
キーワード：VCMA, spintronics, dielectric
Recently, the voltage controlled magnetic anisotropy (VCMA) effect has attracted attention as a low power consumption writing method applicable to magnetic random access memory (MRAM). In the VCMA effect, when a voltage is applied, charges are accumulated at the insulator/ferromagnetic metal interface, which modulates the interfacial orbital magnetic moment, leading to a change of magnetic anisotropy. Therefore, it is desirable to increase the amount of charge accumulated at the interface in order to improve the VCMA efficiency. In fact, there are some reports of using high-k materials as tunnel barrier layers instead of MgO. However, the dielectric constant has not been determined, and the relationship between the dielectric constant and VCMA has not been investigated. In this study, we systematically controlled the dielectric constant of MgO/HfO2 bilayer dielectrics by changing the HfO2 thickness and investigated the relationship between the dielectric constant and the VCMA coefficient.
Multilayered structures consisting of Ta(5)/Ru(10)/Ta(5)/Fe80B20(1.4)/MgO(1.5)/HfO2 (0.95 - 5.0)/Pt(5) (nm) were deposited on thermally oxidized Si substrates. The MgO layer was deposited at room temperature by molecular beam epitaxy, others were deposited by sputtering.
We successfully modulated the the dielectric constant with maintaining the perpendicular magnetic anisotropy at Fe80B20/MgO interface. The dielectric constant increased monotonically with increasing HfO2 thickness. For all samples, clear VCMA effect was observed. The larger the dielectric constant, the larger the VCMA tended to be.
This work was partly based on results obtained from a project, JPNP16007, commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Japan.
Multilayered structures consisting of Ta(5)/Ru(10)/Ta(5)/Fe80B20(1.4)/MgO(1.5)/HfO2 (0.95 - 5.0)/Pt(5) (nm) were deposited on thermally oxidized Si substrates. The MgO layer was deposited at room temperature by molecular beam epitaxy, others were deposited by sputtering.
We successfully modulated the the dielectric constant with maintaining the perpendicular magnetic anisotropy at Fe80B20/MgO interface. The dielectric constant increased monotonically with increasing HfO2 thickness. For all samples, clear VCMA effect was observed. The larger the dielectric constant, the larger the VCMA tended to be.
This work was partly based on results obtained from a project, JPNP16007, commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Japan.