09:45 〜 10:00
▲ [20a-D104-4] Epitaxial strain effect on ferromagnetic resonance and magnetic anisotropy of (Ga0.8,Fe0.2)Sb thin films at room temperature
キーワード：Ferromagnetic Semionductor, Ferromagnetic Resonance, Magnetic Anisotropy Energy
Magnetic anisotropy plays an important role in determining the magnetization direction of ferromagnetic electrodes in spintronic devices. In Mn-doped ferromagnetic semiconductor (FMS) (Ga,Mn)As, control of the magnetic anisotropy between in-plane and perpendicular magnetization using epitaxial growth and strain effects has been demonstrated[1]. However, due to the low Curie temperature (TC < 300K),the (Ga,Mn)As is not suitable for room temperature applications. To overcome this problem, recently we have successfully grown Fe-doped FMS (Ga1-xFex)Sb, which shows TC >300K when x > 0.23 [2,3].
Here, we investigate the magnetic anisotropy of Ga1-xFexSb (x = 0.2, 15nm) grown by low temperature molecular beam epitaxy (LT-MBE) on various different buffer layers: AlSb, GaSb, (In0.5,Ga0.5)As and GaAs. All buffer layers are thick enough (300-500nm) to be lattice-relaxed on semi-insulating GaAs(001) substrates with TC >300K. We carried out ferromagnetic resonance (FMR) and magnetization measurements by superconducting quantum interference device (SQUID) at room temperature, and estimated the magnetic anisotropy parameters. By fitting angle dependence of FMR on magnetic field orientation, we obtained the values of the effective magnetization (Meff), and combining with the saturation magnetization (Ms) measured by SQUID, we estimated the uniaxial anisotropy energy (Ku), shape anisotropy energy (Ksh) and effective anisotropy energy(Keff = Ku + Ksh) of all the Ga1-xFexSb samples grown on different buffers. We define in-plane anisotropy as negative and perpendicular anisotropy as positive values of Ku and Keff. We obtained Ku, Ksh and Keff values vs epitaxial strain ε,which is defined by ε(%) =(a GaFeSb- a buffer)/a GaFeSb x100, where a is the intrinsic lattice constant of each material. We find out when going from tensile (ε=-1.2%) to compressive (ε=+3.9%) strain, the magnitude of Ku initially decreases dramatically, and changes from large negative to small positive. However, Ksh changes from large negative to small negative, making Keff always negative. Therefore, all the (Ga,Fe)Sb films show an in-plane easy magnetization axis which is different from GaMnAs case where easy magnetization axis can be tuned in perpendicular and in-plane axis because of large value of Ku( >> Ksh), in tensile and compressive strain[1].
This work was partly supported by Grants-in-Aid for Scientific Research (No. 26249039, No. 17H04922 and No. 16H02095), CREST of JST, the Spintronics Research Network of Japan (Spin-RNJ), and the Murata Science Foundation.
References:
[1] X.Liu et.al., Phys. Rev. B 67, 205204 (2003).
[2] N.T.Tu et.al., Phys. Rev. B 92, 144403 (2015).
[3] N.T.Tu et.al., Appl. Phys. Lett. 108, 192401(2016).
Here, we investigate the magnetic anisotropy of Ga1-xFexSb (x = 0.2, 15nm) grown by low temperature molecular beam epitaxy (LT-MBE) on various different buffer layers: AlSb, GaSb, (In0.5,Ga0.5)As and GaAs. All buffer layers are thick enough (300-500nm) to be lattice-relaxed on semi-insulating GaAs(001) substrates with TC >300K. We carried out ferromagnetic resonance (FMR) and magnetization measurements by superconducting quantum interference device (SQUID) at room temperature, and estimated the magnetic anisotropy parameters. By fitting angle dependence of FMR on magnetic field orientation, we obtained the values of the effective magnetization (Meff), and combining with the saturation magnetization (Ms) measured by SQUID, we estimated the uniaxial anisotropy energy (Ku), shape anisotropy energy (Ksh) and effective anisotropy energy(Keff = Ku + Ksh) of all the Ga1-xFexSb samples grown on different buffers. We define in-plane anisotropy as negative and perpendicular anisotropy as positive values of Ku and Keff. We obtained Ku, Ksh and Keff values vs epitaxial strain ε,which is defined by ε(%) =(a GaFeSb- a buffer)/a GaFeSb x100, where a is the intrinsic lattice constant of each material. We find out when going from tensile (ε=-1.2%) to compressive (ε=+3.9%) strain, the magnitude of Ku initially decreases dramatically, and changes from large negative to small positive. However, Ksh changes from large negative to small negative, making Keff always negative. Therefore, all the (Ga,Fe)Sb films show an in-plane easy magnetization axis which is different from GaMnAs case where easy magnetization axis can be tuned in perpendicular and in-plane axis because of large value of Ku( >> Ksh), in tensile and compressive strain[1].
This work was partly supported by Grants-in-Aid for Scientific Research (No. 26249039, No. 17H04922 and No. 16H02095), CREST of JST, the Spintronics Research Network of Japan (Spin-RNJ), and the Murata Science Foundation.
References:
[1] X.Liu et.al., Phys. Rev. B 67, 205204 (2003).
[2] N.T.Tu et.al., Phys. Rev. B 92, 144403 (2015).
[3] N.T.Tu et.al., Appl. Phys. Lett. 108, 192401(2016).