Topological Hall effect and magnetic states in the Nowotny chimney ladder compound Cr11⁢Ge19

Abstract

We have investigated the magnetic and charge transport properties of single crystals of the Nowotny chimney ladder compound Cr11⁢Ge19 and mapped out a comprehensive phase diagram reflecting the complicated interplay between the Dzyaloshinskii-Moriya (DM) interaction, the dipolar interaction, and the magnetic anisotropy. We have identified a set of interesting magnetic phases and attributed a finite topological Hall effect to the recently discovered biskyrmion phase. These data also suggest the existence of an antiskyrmion state at finite fields for temperatures just below the magnetic ordering temperature 𝑇𝑐 as indicated by a distinct change in sign of the topological Hall effect. Above 𝑇𝑐, we discovered a region of enhanced magnetic response corresponding to a disordered phase likely existing near the ferromagnetic critical point under small magnetic fields. Strong spin chirality fluctuations are demonstrated by the large value of the topological Hall resistivity persisting up to 1 T, which is most likely due to the existence of the DM interaction. We argue that changes to the topological Hall effect correspond to different topological spin textures that are controlled by magnetic dipolar and DM interactions that vary in importance with temperature.