Half-Metallic Single Crystal CrO 2 Films (JHU MRSEC)
5
1 Half-Metallic Single Crystal CrO 2 Films (JHU MRSEC) ic effects & devices depend directly on spin polari E F NM metal P = 0 E F FM metal 0 < P < 1 E F Half Metal P = 1 P N ( E F ) N ( E F ) N ( E F ) N ( E F ) Density of states g., Cu) (e.g., Co) the ultima
description
Half-Metallic Single Crystal CrO 2 Films (JHU MRSEC). Density of states. NM metal P = 0. FM metal 0 < P < 1. Half Metal P = 1. Spintronic effects & devices depend directly on spin polarization P. (e.g., Cu)(e.g., Co) the ultimate. high R. low R. high R. - PowerPoint PPT Presentation
Transcript of Half-Metallic Single Crystal CrO 2 Films (JHU MRSEC)
1
Half-Metallic Single Crystal CrO2 Films
(JHU MRSEC)Spintronic effects & devices depend directly on spin polarization P
EF
NM metal P = 0
EF
FM metal 0 < P < 1
E F
Half Metal P = 1
P N (EF ) N (EF )
N (EF ) N (EF )Density of states
(e.g., Cu) (e.g., Co) the ultimate
2
high R
low R Spin-valve GMR read-head
Spintronic effects & devices
GMR
high R
low R
TMR
word / sense lines
MRAM
3
Half Metallic FerromagnetsThe ultimate spin-polarized material
•A single spin band
•100% spin polarized
•Integer magnetic moment/unit cellM = µB (nmajority - nminority)
nmajority + nminority = integernmajority = integer
nmajority - nminority = integer
CrO2 (2 µB/unit cell)
Band structure of CrO2
Crystal lattice of CrO2
a
bc
Cr
O
4
Single Crystal [100] CrO2 Films by CVD
Point ContactAndreev Reflection
• In ballistic (Sharvin) limitl > a
Mean free path contact size
CrO2 (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, 180408(R) (2001).
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
