Interplay between magnetic frustration, magnetocrystalline anisotropy and Dzyaloshinskii-Moriya interaction in chiral Co-Zn-Mn alloys

The competition between the magnetic interactions in non-centrosymmetric compounds results in complex phase diagrams. The interplay between symmetric exchange, antisymmetric Dzyaloshinskii-Moriya interaction and crystal anisotropy stabilizes long-range modulated magnetic phases hosting topological skyrmion lattice (SkL). In chiral cubic helimagnets, SkLs are usually stabilized by thermal fluctuations over a narrow region below the magnetic ordering temperature T_c [1]. Recently a new class of chiral alloys CoZnMn with β-Mn structure was found to be SkL-hosting in the large temperature range, even above room temperature [2]. Moreover, an additional low-temperature disordered equilibrium skyrmion phase (LTSk) has been recently found in Co₇Zn₇Mn₆ [3]. Here, by using multiple quantum beam probes, we unveil a direct correlation between the stability of the LTSk – stable far from T_c, and a concomitant enhancement of an underlying magnetic fluctuation rate that is driven by geometric magnetic frustration. The influences of other leading skyrmion stability mechanisms, such as those derived from thermal fluctuations [1] and low T cubic anisotropies [4], are shown to be weak in this system. We therefore advance the existing of a fundamental mechanism for stabilizing topological phase in Co₇Zn₇Mn₆ that draws upon magnetic frustration as the key ingredient [6]. The elaboration of a such a stability mechanism could find general relevance in the ongoing research topological magnetic textures amongst the multifarious frustrated magnets.

[1] Mühlbauer, S. et al., Science 323, 915–919 2009

[2] Tokunaga, Y., et al., Nat. Commun., 6, 7638 2015

[3] Karube, K., et al., Science Adv., 4(9), eaar7043 2018

[4] Chacon, A. et al., Nat. Phys. 14, 936 2018

[5] Ukleev, V., et al., npj Quantum Mat. 6, 40 2021