Temperature dependent magnetization and magnetic phases of

1. Enhanced electron spin-splitting, Uoσ Density of States (DOS) ● the DOS deviates from the famous step-like (B→0) form. spin-spin exchange interaction between s- or p- conduction band electrons and d- electrons of Μn+2 cations proportional to the cyclotron gap Not only the general shape of the DOS varies , but this effect is also quantitative. • for anytype ofinterplaybetween spatial and magnetic confinement Low temperatures. spin-splitting maximum, ~ 1/3 of conduction band offset Higher temperatures. spin-splitting decreases enhanced contribution of spin-up electrons Feedback mechanism due tondown(r) - nup(r). e.g. n-doped DMS ZnSe / Zn1-x-yCdxMnySe / ZnSe QWs in-plane magnetic field Magnetization L = 10 nm (spatial confinement dominates) Dispersion, Density of States, Free Energy Magnetic Phases, Spin Polarization • Density of States diverges significantly from • ideal step-like 2DEGform •  severe changes to physical properties: • spin-subband populations • internal energy, U • free energy, F • Shannon entropy, S • magnetization, M A single behavior ofInternal EnergyFree EnergyEntropy ~ parabolic spin subbandsincrease Bmore flat dispersion few % DOS increase Spin polarization tuned by varying temperature and magnetic field. L = 30 nm(drastic dispersion modification) Spin-subband dispersion and DOS Spin-subband Populations Internal energy Free Energy Entropy L = 30 nm narrow L = 10 nm, almost parabolic dispersion + Depopulation of higher spin-subband L = 60 nm(~ spin-down bilayer system) Spin-subband dispersion and DOS L = 60 nm, ~ bilayer system Epilogue - Outlook ☺ Magnetization of conduction-band, narrow to wide NMS/DMS/NMS structures with in-plane B. ☺If strong competition (spatial vs. magnetic) confinement  impressive fluctuation of M. ☺Spin polarization tuned by varying T and B. ♫ In this poster we have approximated ndown(r) – nup(r) by (Ns,down - Ns,up) / L … ♫A more orderly study of the magnetic phases will be hopefully presented … Spin-subband Populations Internal Energy Free Energy Entropy L = 60 nm + Depopulation of higher spin-subband Temperature dependent magnetization and magnetic phases of conduction-band dilute-magnetic-semiconductor quantum wells with non-step-like density of states Constantinos Simserides 1,21 University of Athens, Physics Department, Solid State Section, Athens, Greece 2 Leibniz Institute for Neurobiology, Special Lab for Non-Invasive Brain Imaging, Magdeburg, Germany SUMMARY We study the magnetization and the magnetic phases of II-VI-based n-doped non-magnetic-semiconductor (NMS) / narrow to wide dilute-magnetic-semiconductor(DMS) / n-doped NMS quantum wells under in-plane magnetic field. The parallel magnetic field is used as a tool, in order to achieve non-step-like density of states in these -appropriate for conduction-band spintronics- structures. conduction band, narrow to wide, DMS QWs RESULTS AND DISCUSSION considerable fluctuation of M (if vigorous competition between spatial and magnetic confinement) L = 10 nm : almost parabolic dispersion L = 30 nm : strong competition between spatial and magnetic confinement L = 60 nm : ~ spin-down bilayer system Bibliography [1] H. Ohno, J. Magn. Magn. Mater. 272-276, 1 (2004); J. Crystal Growth 251, 285 (2003). [5] S. P. Hong, K. S. Yi, J. J. Quinn, Phys. Rev. B 61, 13745 (2000). [9] H. W. Hölscher, A. Nöthe and Ch. Uihlein, Phys. Rev. B 31, 2379 (1985). [2] M. Syed, G. L. Yang, J. K. Furdyna, et al, Phys. Rev. B 66, 075213 (2002). [6] H. J. Kim and K. S. Yi, Phys. Rev. B 65, 193310 (2002). [10] B. Lee, T. Jungwirth, A. H. MacDonald, Phys. Rev. B 61, 15606 (2000). [3] S. Lee, M. Dobrowolska, J. K. Furdyna, and L. R. Ram-Mohan, Phys. Rev. B 61, 2120 (2000). [7] C. Simserides, Physica E 21, 956 (2004). [11] L. Brey and F. Guinea, Phys. Rev. Lett. 85, 2384 (2000). [4] C. Simserides, J. Comput. Electron. 2, 459 (2003); Phys. Rev. B 69, 113302 (2004). [8] H. Venghaus, Phys. Rev. B 19, 3071 (1979).