Anisotropy-induced depinning in the Zn-substituted skyrmion host Cu2OSeO3

Abstract

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Position-dependent stability and lifetime of the skyrmion state in nickel-substituted Cu2OSeO3

“…2(e) and 2(f), we see that the magnitude of the peaks are reduced in the Ni-substituted sample. Similar behavior was previously reported in a Zn-substituted sample, where it was attributed to pinning effects introduced by the dopant [47]. Furthermore, there are two peaks seen in the ZFC data for both samples.…”

“…These have previously been attributed to the reorientation of different helical domains in the Cu 2 OSeO 3 when the field is applied along the [110]. Significantly, our data suggest that this reorientation occurs in both the Nisubstituted and pristine samples, while it has been reported that this feature is suppressed by Zn substitution [47]. This suggests that the magnetic Ni substitution modifies the phase transitions in Cu 2 OSeO 3 in a different manner compared to nonmagnetic Zn substitution.…”

Toggle-switch-like crossover between two types of isolated skyrmions within the conical phase of cubic helimagnets

“…In particular, uniaxial anisotropy of the easy-axis type 65 , which does not affect the ideal single-harmonic type of the magnetization rotation in the conical spiral but just leads to the gradual closing of the cone, grants the thermodynamical stability of the V-SkL in a broad region of theoretical and experimental phase diagrams [66][67][68] . Cubic anisotropy also stabilizes V-SkLs but for specific directions of the applied magnetic field 38,[69][70][71] . This anisotropy deforms the ideal conical configuration as the magnetization tends to deviate from the ideal conical surface trying to embrace the easy axes and to avoid the hard directions.…”

Experimental Evidence of a change of Exchange Anisotropy Sign with Temperature in Zn-Substituted Cu2OSeO3

“…Unlike in the related compound FeGe, this change of sign does not induce a reorientation of the zero-field magnetic helix. This demonstrates that the 4 th order MCA also increases in magnitude with decreasing temperature, greater that the AEI in order to stabilize the zero-field magnetic helices along the 1 0 0 directions at all temperatures [37]. Our findings provide insight into the low temperature behavior of Cu 2 OSeO 3 that will be essential for complete understanding of the creation and stabilization mechanisms of the recently discovered LTS and TC phases within pristine Cu 2 OSeO 3 .…”

“…A zinc-substituted sample was chosen for our study due to the reduction of the exchange interaction compared to pristine Cu 2 OSeO 3 , resulting in a greater value of q [37]. Previously, we have shown strong similarities of the magnetic behavior between Zn-substituted and pristine samples [37], and hence we expect our results here will extend to pristine samples. The time-of-flight neutron diffraction data was reduced with Mantid [40], using scattered neutron wavelengths between 0.9 and 13.5 A.…”