1:30 PM - 3:30 PM
[19p-P1-60] Spacer layer thickness dependence of CPP-GMR effects in Co2(Fe-Mn)Si/L12-Ag-Mg/Co2(Fe-Mn)Si devices
Keywords:GMR,Heusler alloy
Introduction: Current perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices are of interests for applying reading head of hard disk drives (HDDs). CPP-GMR devices with low resistance-area product (RA) and high magnetoresistance (MR) ratio are required for the future HDD applications [1]. We previously reported ΔRA value of 17 mWmm2 in the CPP-GMR devices using a Ag83Mg17 spacer layer with partial L12-ordering and Co2Fe0.4Mn0.6Si (CFMS) electrodes, which was larger than that of the conventional devices with a Ag spacer layer [2]. In this work, we prepared a well ordered L12 Ag78Mg22 spacer layer for the CFMS/Ag-Mg/CFMS devices and investigated the spacer layer thickness dependence of CPP-GMR effects.
Experimental: A stacking structure of the samples was; MgO (100) sub./Cr (20 nm)/Ag (40 nm)/CFMS (20 nm)/Ag78Mg22 (t nm)/CFMS (7 nm)/Ag (2 nm)/Au (5 nm). All layers were deposited at room temperature, and in situ post-annealing was performed at 650ºC and 500ºC, after the depositions of Cr and the upper CFMS layers, respectively. The thicknesses of the Ag78Mg22 spacer layer, t, were 2, 3, and 5 nm. The crystal structure was characterized using reflection high energy electron diffraction (RHEED) technique. MR effects were measured by direct current four-terminal method at room temperature.
Results: In situ RHEED observation was performed for the top CFMS surface, and the epitaxial growth and the L21-ordering of the CFMS were confirmed regardless of the spacer layer thickness. RA values of the CPP-devices were determined from the plots of the junction resistances at the parallel magnetization configuration (Rp) as a function of the inverse junction area (1/A). RA values and MR ratios increased with the spacer layer thickness. The maximum values of MR ratio and ΔRA were 56% and 20 mWmm2 for t = 5 nm. CPP-GMR effects of the devices with thicker spacer layer are to be discussed at the presentation.
Acknowledgements: This work was supported by the Hattori Hokokai Foundation, ImPACT program of the Council for Science, Technology and Innovation, and a KAKENHI (No. 25220910) from JSPS.
References:
[1] M. Takagishi, et al., IEEE Trans. Magn. 46, 2086 (2010).
[2] H. Narisawa, et al., Appl. Phys. Express 8, 063008 (2015).
Experimental: A stacking structure of the samples was; MgO (100) sub./Cr (20 nm)/Ag (40 nm)/CFMS (20 nm)/Ag78Mg22 (t nm)/CFMS (7 nm)/Ag (2 nm)/Au (5 nm). All layers were deposited at room temperature, and in situ post-annealing was performed at 650ºC and 500ºC, after the depositions of Cr and the upper CFMS layers, respectively. The thicknesses of the Ag78Mg22 spacer layer, t, were 2, 3, and 5 nm. The crystal structure was characterized using reflection high energy electron diffraction (RHEED) technique. MR effects were measured by direct current four-terminal method at room temperature.
Results: In situ RHEED observation was performed for the top CFMS surface, and the epitaxial growth and the L21-ordering of the CFMS were confirmed regardless of the spacer layer thickness. RA values of the CPP-devices were determined from the plots of the junction resistances at the parallel magnetization configuration (Rp) as a function of the inverse junction area (1/A). RA values and MR ratios increased with the spacer layer thickness. The maximum values of MR ratio and ΔRA were 56% and 20 mWmm2 for t = 5 nm. CPP-GMR effects of the devices with thicker spacer layer are to be discussed at the presentation.
Acknowledgements: This work was supported by the Hattori Hokokai Foundation, ImPACT program of the Council for Science, Technology and Innovation, and a KAKENHI (No. 25220910) from JSPS.
References:
[1] M. Takagishi, et al., IEEE Trans. Magn. 46, 2086 (2010).
[2] H. Narisawa, et al., Appl. Phys. Express 8, 063008 (2015).