Temperature dependent magnetization and magnetic phases of conduction-band dilute-magnetic-semiconductor quantum wells with non-step-like density of states Constantinos Simserides 1,2 1 University of Athens, Physics Department, Solid State Section, Athens, Greece 2 Leibniz Institute for Neurobiology, Special Lab for Non-Invasive Brain Imaging, Magdeburg, Germany Density of States (DOS) ● the DOS deviates from the famous step-like (B→0) form. Not only the general shape of the DOS varies, but this effect is also quantitative. for any type of interplay between spatial and magnetic confinement RESULTS AND DISCUSSION Density of States diverges significantly from ideal step-like 2DEG form  severe changes to physical properties: spin-subband populations internal energy, U free energy, F Shannon entropy, S magnetization, M ~ parabolic spin subbands increase B  more flat dispersion  few % DOS increase A single behavior of Internal Energy Free Energy Entropy L = 10 nm (spatial confinement dominates) L = 30 nm (drastic dispersion modification) Spin-subband dispersion and DOS Spin-subband Populations Internal energy Free Energy Entropy L = 30 nm + Depopulation of higher spin-subband L = 60 nm (~ spin-down bilayer system) Spin-subband dispersion and DOS L = 60 nm Spin-subband Populations Internal Energy Free Energy Entropy + Depopulation of higher spin-subband Bibliography [1] H. Ohno, J. Magn. Magn. Mater , 1 (2004); J. Crystal Growth 251, 285 (2003).[5] S. P. Hong, K. S. Yi, J. J. Quinn, Phys. Rev. B 61, (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, (2002).[6] H. J. Kim and K. S. Yi, Phys. Rev. B 65, (2002). [10] B. Lee, T. Jungwirth, A. H. MacDonald, Phys. Rev. B 61, (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, (2004).[8] H. Venghaus, Phys. Rev. B 19, 3071 (1979). 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 n down (r) – n up (r) by (N s,down - N s,up ) / L … ♫ A more orderly study of the magnetic phases will be hopefully presented … Dispersion, Density of States, Free Energy 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 Magnetization Enhanced electron spin-splitting, U oσ 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 to n down (r) - n up (r). spin-spin exchange interaction between s- or p- conduction band electrons and d- electrons of Μn +2 cations proportional to the cyclotron gap in-plane magnetic field 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,DMSQWs Spin polarization tuned by varying temperature and magnetic field. narrow L = 10 nm, almost parabolic dispersion Magnetic Phases, Spin Polarization L = 60 nm, ~ bilayer system e.g. n-doped DMS ZnSe / Zn 1-x-y Cd x Mn y Se / ZnSe QWs