Spin polarization and magnetization of conduction-band dilute-magnetic-semiconductor quantum wells with non-step-like density of states

Abstract

Abstract. We study the magnetization, M , and the spin polarization, ζ, of n-doped nonmagnetic-semiconductor (NMS) / narrow to wide dilute-magnetic-semiconductor (DMS) / ndoped NMS quantum wells, as a function of the temperature, T , and the in-plane magnetic field, B. Under such conditions the density of states (DOS) deviates from the occasionally stereotypic step-like form, both quantitatively and qualitatively. The DOS modification causes an impressive fluctuation of M in cases of vigorous competition between spatial and magnetic confinement. At low T , the enhanced electron spin-splitting, Uoσ, acquires its bigger value. At higher T , Uoσ decreases, augmenting the influence of the spin-up electrons. Increasing B, Uoσ increases and accordingly electrons populate spin-down subbands while they abandon spin-up subbands. Furthermore, due to the DOS modification, all energetically higher subbands become gradually depopulated. . IntroductionDuring the last few years, the advancement of growth, characterization and understanding of transition-metal-doped III-V semiconductors has been impressive. In magnetic semiconductor heterostructures based e.g. on (Ga,Mn)As, Mn substitutes a small fraction of cations providing holes and local magnetic moments. Many new phenomena have been accordingly brought to light e.g. tunnel magnetoresistance, spin-dependent scattering, interlayer coupling due to carrier polarization, electrical electron and hole spin injection, and electric field control of ferromagnetism [1]. Most of the structures used are based on III-V magnetic semiconductors like (In,Mn)As and (Ga,Mn)As which utilize the valence band [1]. The highest ferromagnetic transition temperature, T C , reported so far for III-V-based valence-band magnetic semiconductors is 110 K for (Ga,Mn)As and 60 K for (In,Mn)As, for bulk materials, while T C can reach 150 K for some heterostructures [1].On the other hand, in II-VI materials, Mn provides only local magnetic moments, and the corresponding heterostructures e.g. ZnSe/Zn 1−x−y Cd x Mn y Se/ZnSe utilize the conduction band.