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1 Half-Metallic Single Crystal CrO 2 Films (JHU MRSEC) Spintronic effects & devices depend directly on spin polarization P NM metal P = 0 FM metal 0 <

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Presentation on theme: "1 Half-Metallic Single Crystal CrO 2 Films (JHU MRSEC) Spintronic effects & devices depend directly on spin polarization P NM metal P = 0 FM metal 0 <"— Presentation transcript:

1 1 Half-Metallic Single Crystal CrO 2 Films (JHU MRSEC) Spintronic effects & devices depend directly on spin polarization P NM metal P = 0 FM metal 0 < P < 1 Half Metal P = 1 Density of states (e.g., Cu)(e.g., Co) the ultimate

2 2 high R low R Spin-valve GMR read-head Spintronic effects & devices GMR high R low R TMR MRAM

3 3 Half Metallic Ferromagnets The ultimate spin-polarized material A single spin band 100% spin polarized Integer magnetic moment/unit cell M = µ B (n majority - n minority ) n majority + n minority = integer n majority = integer n majority - n minority = integer CrO 2 (2 µ B /unit cell) Band structure of CrO 2 Crystal lattice of CrO 2

4 4 Single Crystal [100] CrO 2 Films by CVD Point Contact Andreev Reflection In ballistic (Sharvin) limit l > a Mean free path contact size CrO 2 (P = 98.4%) is half metallic ! Ji, Strijkers, Yang, Chien, Byers, Anguelouch, Xiao, and Gupta, Phys. Rev. Lett. 86, 5585 (2001). Anguelouch, Gupta, Xiao, Abraham, Ji, Ingvarsson, and Chien, Phys. Rev. B 64, (R) (2001).

5 5 Significance of Half-Metallic Ferromagnets Ultimate magnetic tunnel junctions: infinite TMR Conducting Insulating Perfect spin injector for semiconductors and metals Physics of a single spin band


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