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▼ [17a-501-9] Anisotropic magnetization-direction dependence of band structure in the perovskite oxide La0.6Sr0.4MnO3
Keywords:spintronics, oxide, magnetic anisotropy
For efficient gate-electric-field control of the magnetization direction of ferromagnetic (FM) thin films, it is required to understand the carrier-energy dependence of the magnetic anisotropy (MA). Tunneling anisotropic magnetoresistance (TAMR), which reflects the density of states (DOS) of FM thin films, is specifically suitable for this purpose. Because the magnetization-direction dependence of DOS is directly related to MA in FM materials, by measuring TAMR for various magnetic-field directions at various bias voltages, one can obtain the energy-resolved map of the MA of FM thin films.
In this study, we investigate the energy-dependence of the MA of the perovskite oxide La0.6Sr0.4MnO3 (LSMO), which is a promising spintronic material due to its half-metallic band structure [1], high Curie temperature (~ 370 K), and colossal magnetoresistance [2]. The used tunnel device structure consists of LSMO (40 unit cell (uc))/ LaAlO3 (LAO, 4 uc) grown on a Nb-doped (0.5 wt%) SrTiO3(001) (Nb:STO) substrate by molecular beam epitaxy. For our tunneling transport measurements, a 50-nm thick Au film was deposited on top of the sample, and mesa diodes with the size of 600×700 mm2 were formed. The bias polarity was defined so that electrons flow from Nb:STO to LSMO in positive V. We measured the change in the tunneling conductance delta dI/dV (%) with V ranging from –0.5 to +0.5 V while rotating a magnetic field of 1 T in the plane. By analyzing the TAMR data, we find that there are a two-fold symmetry component C2[010] along the [010] axis, a weak four-fold symmetry component C4<110> along the <110> axes, and a two-fold symmetry component C2[110] along the [110] axis. C2[110] has not been reported before in LSMO, which indicates that it is a specific component to the interface. With decreasing V, the two-fold magnetic easy axis along the [110] direction is rotated by 90 degrees at V ≈ –0.2 V. We discuss the origins of this complex MA and its relation to the band structure of LSMO.
References:[1] J. Park et al., Nature 392, 794 (1998). [2] A. Urushibara et al., PRB 51, 20 (1995).
This work was partly supported by Grants-in-Aid for Scientific Research, Project for Developing Innovation Systems of MEXT, and Spintronics Research Network of Japan (Spin-RNJ).
In this study, we investigate the energy-dependence of the MA of the perovskite oxide La0.6Sr0.4MnO3 (LSMO), which is a promising spintronic material due to its half-metallic band structure [1], high Curie temperature (~ 370 K), and colossal magnetoresistance [2]. The used tunnel device structure consists of LSMO (40 unit cell (uc))/ LaAlO3 (LAO, 4 uc) grown on a Nb-doped (0.5 wt%) SrTiO3(001) (Nb:STO) substrate by molecular beam epitaxy. For our tunneling transport measurements, a 50-nm thick Au film was deposited on top of the sample, and mesa diodes with the size of 600×700 mm2 were formed. The bias polarity was defined so that electrons flow from Nb:STO to LSMO in positive V. We measured the change in the tunneling conductance delta dI/dV (%) with V ranging from –0.5 to +0.5 V while rotating a magnetic field of 1 T in the plane. By analyzing the TAMR data, we find that there are a two-fold symmetry component C2[010] along the [010] axis, a weak four-fold symmetry component C4<110> along the <110> axes, and a two-fold symmetry component C2[110] along the [110] axis. C2[110] has not been reported before in LSMO, which indicates that it is a specific component to the interface. With decreasing V, the two-fold magnetic easy axis along the [110] direction is rotated by 90 degrees at V ≈ –0.2 V. We discuss the origins of this complex MA and its relation to the band structure of LSMO.
References:[1] J. Park et al., Nature 392, 794 (1998). [2] A. Urushibara et al., PRB 51, 20 (1995).
This work was partly supported by Grants-in-Aid for Scientific Research, Project for Developing Innovation Systems of MEXT, and Spintronics Research Network of Japan (Spin-RNJ).