Helical magnetic order in MnSi thin films

We present a study of the magnetic structure of crystalline MnSi(111) thin films grown by molecular beam epitaxy. A combination of polarized neutron reflectometry (PNR) and superconducting quantum interference device magnetometry show that the films have helical magnetic order with a pitch vector Q along the film normal. The helix wavelength of 2π/Q=13.9±0.1 nm is found to be independent of thickness below 40 nm. PNR shows that the magnetic structure has both left-handed and right-handed chiralities due to the presence of inversion domains observed by transmission electron microscopy.