Chiral modulations and reorientation effects in MnSi thin films

Abstract

We present an experimental and theoretical investigation of the influence of a uniaxial magnetocrystalline anisotropy on the magnetic textures that are formed in a chiral magnetic system. We show that the epitaxially induced tensile stress in MnSi thin films grown on Si (111) creates an easy-plane uniaxial anisotropy. The magnetoelastic shear stress coefficient is derived from SQUID magnetometry measurements in combination with transmission electron microscopy and x-ray diffraction data. Density functional calculations of the magnetoelastic coefficient support the conclusion that the uniaxial anisotropy originates from the magnetoelastic coupling. Theoretical calculations based on a Dzyaloshinskii model that includes an easy-plane anisotropy predict a variety of modulations to the magnetic order that are not observed in bulk MnSi crystals. Evidence for these states is found in the magnetic hysteresis and polarized neutron reflectometry measurements.

Neutron study of in-plane skyrmions in MnSi thin films

“…A spin polarization in excess of 95% was produced by a CoFe/Si supermirror and a Mezei-type precession spin flipper. Previous measurements showed that the spin-flip signal is negligible due to the cancelling ef- fects of the bi-chiral magnetic domains 32 . Therefore we measured the spin-up, R + and spin-down, R − reflectivities without an analyzer in order to increase the signalto-noise ratio.…”

“…4(b). The simulations include the nuclear scattering length densities obtained from combined x-ray reflectometry and PNR measurements 32 . To make the comparison with model calculations more clear, the µ 0 H = 0.7 T data are presented in terms of the spin asymmetry, α = (R + −R − )/(R + +R − ), in the left-hand panel of Fig.…”

“…A hard-axis out-ofplane magnetocrystalline anisotropy exists in the case of MnSi/Si(111) 32 . Although numerical simulations show that finite size effects can lead to stable skyrmion states for small enough values of the hard-axis anisotropy and film thickness 18 , no evidence for skyrmions are found in magnetometry or electron transport measurements in .…”

“…Anisotropy is of importance for understanding the magnetic structure of chiral magnetic epilayers grown on Si(111) substrates, including MnSi [30][31][32] , FeGe 33 , Fe x Co 1−x Si 34,35 and MnGe 36 .…”

Partial phase transition and quantum effects in helimagnetic films under an applied magnetic field

“…Phase transitions in thin films with non-collinear ground states have been only recently studied [15][16][17][18]25]. MC simulations of a helimagnetic thin film [26] and a few experiments in helimagnets [27,28] have also been carried out. These investigations were motivated by the fact that helical magnets present a great potential of applications in spintronics with spindependent electron transport [29][30][31].…”