Resonant X-ray magnetic reflectometry of skyrmions and helicoids in MnGe thin films

MnGe is a chiral magnetic material that potentially possesses multiple interesting topological states. Although the cubic B20 phase is not thermodynamically stable in bulk form, single orientation films can be grown on Si substrates. In out-of-plane magnetic fields, the low temperature phase possibly forms a 3-dimensional ‘spin-hedgehog’ lattice. The in-plane magnetic phase diagram is not fully understood. We proposed to use X-ray resonant magnetic reflectometery to measure the magnetic structure of high-quality MnGe films grown by molecular beam epitaxy on Si(111) substrates to reveal the structure of an unidentified phase in a pocket near the magnetic ordering temperature, which may correspond to 2-dimensional topological structures known as skyrmions. By exploring a series of film thicknesses, we will investigate how finite size effects affect the competition between helicoids and skyrmions and potentially find evidence for a novel chiral interaction predicted to exist in MnGe.