Canted antiferromagnet in the bilayer nu=2 quantum Hall system

In a bilayer quantum Hall system at total Landau level filling factor nu=2, the competing spin and layer degrees of freedom is predicted to lead to various magnetic phases: the ferromagnetic state, the canted antiferromagnetic state, and the spin-singlet state. However, direct information on the spin configuration has not been reported.
In this work, we investigate electron spin states by using a current pumped and resistively-detected NMR technique. Knight shift and nuclear spin relaxation measurements show that in-plane electronic spin order develops when the out-of-plane spin polarization is intermediate values between full and null. The result is evidence for the electron spin canting between the ferromagnetic and spin-singlet states.
[Link]

>>back

Electron spin polarization (top panel) and the nuclear spin relaxation rate 1/T1 (bottom panel) in the bilayer nu=2 quantum Hall system as a function of the density imbalance (delta). The increase in 1/T/1 with decreasing temperature observed at intermediate delta is a hallmark for the development of the in-plane electronic spin order. The combination of the spin polarization and 1/T1 data reveal the evolution of the canted antiferromagnetic (CAF) spin configuration between the ferromagnetic (F) and spin-singlet (SS) states.