III-V based magnetic semiconductors show hole-induced ferromagnetism [1], and their magnetic properties can be modulated by the application of electric fields E through the change of hole concentration p [2]. It was reported that the relationship between the Curie temperature T_C and p for thin (Ga,Mn)As layers is expressed as T_C ∝ p^0.2, where p was controlled by using a field-effect structure by the application of E [3]. The result can be reproduced by an adapted p-d Zener model with non-uniform hole distribution due to the depletion region at the interface between gate insulator and (Ga,Mn)As [3,4]. Since the exponent is expected to depend on the material dependent pinning position of the Fermi level at the interface [5], in this work, we adopt (Ga,Mn)Sb as a channel layer in a field-effect structure.
  5 nm-thick (Ga,Mn)Sb layers are grown by low temperature molecular beam epitaxy on 5 nm GaSb / 300 nm A_0.8Ga_0.2Sb / 10 nm AlSb onto semi-insulating GaAs (001) substrate [6,7]. The field-effect structure has a Hall-bar shape for transport measurements. The measurements are performed under perpendicular magnetic field μ₀H (|μ₀H| < 0.5 T, μ₀: permeability in vacuum) at various temperature T and E. We determine p from the E dependence of the channel conductivity and T_C from the H dependence of Hall resistance by making the Arrott plots. We determine to be the exponent γ ~ 1 in T_C ∝ p^γ, and show that it can be reproduced by the adapted p-d Zener model with hole accumulation at the interface of (Ga,Mn)Sb and gate insulator, which is consistent with the Fermi energy pinning position of p-GaSb at the interface [8]. We show also that a perpendicular magnetic anisotropy of (Ga,Mn)Sb is E dependent.
We would like thank M. Sawicki and T. Dietl for discussion. This work was supported in part by the FIRST program of JSPS.

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[2] H. Ohno, D. Chiba, F. Matsukura, T. Omiya, E. Abe, T. Dietl, Y. Ohno, and K. Ohtani, Nature 408, 944 (2000).
[3] Y. Nishitani, D. Chiba, M. Endo, M. Sawichi, F. Matsukura, T. Dietl, and H. Ohno, Phys. Rev. B 81, 045208 (2010).
[4] M. Sawicki, D. Chiba, A. Korbecka, Y. Nishitani, J. A. Majewski, F. Matsukura, T. Dietl, and H. Ohno, Nature Phys. 6, 22 (2010).
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[8] H. Hasegawa, H. Ohno, and T. Sawada, Jpn. J. Appl. Phys. 25, L265 (1986).

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