TY - JOUR
T1 - The role of structure on magneto-transport properties of Heusler Co 2MnSi films deposited on MgO(001)
AU - Tal, N.
AU - Mogilyanski, D.
AU - Kovács, A.
AU - Naganuma, H.
AU - Tsunegi, S.
AU - Oogane, M.
AU - Ando, Y.
AU - Kohn, A.
N1 - Funding Information:
We thank Dr. Vladimir Ezersky for assistance with TEM experiments. This research was partly supported by ASPIMATT from JST and for World-Leading Innovative R&D on Science and Technology (FIRST Program) by JSPS program.
PY - 2013/10/28
Y1 - 2013/10/28
N2 - We present an experimental study identifying structural reasons that degrade spin-polarization of Co2MnSi thin films deposited on MgO(001) substrates. Through the fabrication of magnetic tunnel junctions, we measure a range of values for tunneling magneto-resistance (TMR) ratios following post-deposition annealing and epitaxial crystallization of the Heusler film. These TMR ratios reflect qualitatively the change in spin polarization of the Co2MnSi thin films. Low-temperature annealing results in low spin-polarization due to a high fraction of an amorphous phase. As annealing temperatures increase, the fraction of L21 and B2 chemically ordered phases increases, thus improving significantly the spin-polarization. However, for samples annealed at higher temperatures, significant degradation in the cubic magneto-crystalline anisotropy is observed, which we attribute to the detection of manganese diffusion into the MgO substrate. This Mn diffusion is manifested in a reduction of the value of the TMR ratio, namely, the spin polarization. Additionally, the maximum TMR ratio measured here, approximately 65% at room-temperature, is limited because the semi-coherent interface of Co2MnSi with the MgO substrate terminates with a Mn-Si layer.
AB - We present an experimental study identifying structural reasons that degrade spin-polarization of Co2MnSi thin films deposited on MgO(001) substrates. Through the fabrication of magnetic tunnel junctions, we measure a range of values for tunneling magneto-resistance (TMR) ratios following post-deposition annealing and epitaxial crystallization of the Heusler film. These TMR ratios reflect qualitatively the change in spin polarization of the Co2MnSi thin films. Low-temperature annealing results in low spin-polarization due to a high fraction of an amorphous phase. As annealing temperatures increase, the fraction of L21 and B2 chemically ordered phases increases, thus improving significantly the spin-polarization. However, for samples annealed at higher temperatures, significant degradation in the cubic magneto-crystalline anisotropy is observed, which we attribute to the detection of manganese diffusion into the MgO substrate. This Mn diffusion is manifested in a reduction of the value of the TMR ratio, namely, the spin polarization. Additionally, the maximum TMR ratio measured here, approximately 65% at room-temperature, is limited because the semi-coherent interface of Co2MnSi with the MgO substrate terminates with a Mn-Si layer.
UR - http://www.scopus.com/inward/record.url?scp=84887269854&partnerID=8YFLogxK
U2 - 10.1063/1.4826908
DO - 10.1063/1.4826908
M3 - Article
AN - SCOPUS:84887269854
SN - 0021-8979
VL - 114
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 16
M1 - 163904
ER -