Cubic magnetic anisotropy in $B$20 magnets: Interplay of anisotropy and magnetic order in Fe${}_{1-x}$Co${}_x$Si

Abstract

The metallic systems MnSi and Fe${}_{1-x}$Co${}_x$Si are known to feature a generic magnetic phase diagram primarily determined by the isotropic exchange and Dzyaloshinskii-Moriya interactions. However, additional weaker anisotropies, lowest in the hierarchy of energy scales, play a crucial role: they determine the relative order of phases in the phase diagram and may even enable skyrmion stability far below the ordering temperature. Among cubic B20 helimagnets, the insulator Cu${}_2$OSeO${}_3$ is currently the only known example exhibiting a low-temperature, anisotropy-induced skyrmion pocket. In this manuscript, we present a systematic study of cubic magnetocrystalline anisotropy by means of angle-resolved SQUID magnetization measurements in MnSi and Fe${}_{1-x}$Co${}_x$Si ($0.08\le x\le 0.70$) single crystals and provide quantitative values of the anisotropy constants. For Fe${}_{1-x}$Co${}_x$Si, the cubic anisotropy is found to be strongly dependent on the Co concentration $x$. In particular, for low Co concentrations ($x\sim 0.10$), the anisotropy is sufficiently strong to stabilize a low-temperature skyrmion lattice, in agreement with theoretical predictions. This finding suggests that Fe${}_{1-x}$Co${}_x$Si may represent the first chiral metallic system to exhibit a low-temperature skyrmion phase controllably stabilized by cubic anisotropy for specific directions of the magnetic field.

References in corpus (22)

• Skyrmion Lattice in a Chiral Magnet
• Topological Hall effect in the A-phase of MnSi
• Skyrmion Lattice in a Doped Semiconductor
• Fluctuation-induced first-order phase transition in Dzyaloshinskii-Moriya helimagnets
• Large Anomalous Hall effect in a silicon-based magnetic semiconductor
• Magnetic phase diagram of MnSi inferred from magnetization and ac susceptibility
• Magnetoresistance From Quantum Interference Effects in Ferromagnets
• Formation and rotation of skyrmion crystal in the chiral-lattice insulator Cu2OSeO3
• Observation of two independent skyrmion phases in a chiral magnetic material
• Specific heat of the skyrmion lattice phase and field-induced tricritical point in MnSi
• Giant generic topological Hall resistivity of MnSi under pressure
• History dependence of the magnetic properties of single-crystal Fe${}_{1-x}$Co${}_x$Si
• Low spin wave damping in the insulating chiral magnet Cu${}_2$OSeO${}_3$
• Thermodynamic evidence of a second skyrmion lattice phase and tilted conical phase in Cu${}_2$0SeO${}_3$
• Reorientations, relaxations, metastabilities and multidomains of skyrmion lattices
• Weak crystallization of fluctuating skyrmion textures in MnSi
• Response of the skyrmion lattice in MnSi to cubic magnetocrystalline anisotropies
• Evolution of magneto-crystalline anisotropies in Mn${}_{1-x}$Fe${}_x$Si and Mn${}_{1-x}$Co${}_x$Si as inferred from small-angle neutron scattering and bulk properties
• Magnetization under High Pressure in MnSi
• Anisotropic magneto-crystalline coupling of the skyrmion lattice in MnSi
• Physical properties of (Mn,Co)Si
• Disordered 2D ferromagnetism at the surface of FeSi