Room-temperature skyrmion phase in bulk Cu ₂ OSeO ₃ under high pressures

Abstract

A skyrmion state in a noncentrosymmetric helimagnet displays topologically protected spin textures with profound technological implications for high-density information storage, ultrafast spintronics, and effective microwave devices. Usually, its equilibrium state in a bulk helimagnet occurs only over a very restricted magnetic field–temperature phase space and often in the low-temperature region near the magnetic transition temperature Tc. We have expanded and enhanced the skyrmion phase region from the small range of 55 to 58.5 K to 5 to 300 K in single-crystalline Cu2OSeO3 by pressures up to 42.1 GPa through a series of phase transitions from the cubic P213, through orthorhombic P212121 and monoclinic P21, and finally to the triclinic P1 phase, using our newly developed ultrasensitive high-pressure magnetization technique. The results are in agreement with our Ginzburg–Landau free energy analyses, showing that pressures tend to stabilize the skyrmion states and at higher temperatures. The observations also indicate that the skyrmion state can be achieved at higher temperatures in various crystal symmetries, suggesting the insensitivity of skyrmions to the underlying crystal lattices and thus the possible more ubiquitous presence of skyrmions in helimagnets.

Single crystal growth and structural, magnetic, and magnetoelectric properties in spin-frustrated bow-tie lattice of α-Cu5O2(SeO3)2Cl2

“…This has resulted in fascinating properties such as multiferroic, magnetoelectric effect and skyrmionic phase. 8,24,[27][28][29][31][32][33][35][36][37]40,48,50,51 Lone pair Se 4+ ions and electron negative halide atoms serve as chemical scissors that can stabilize the low-dimensional magnetic lattice with spin frustration. 12 Several compounds in the CuO-CuCl 2 -SeO 2 ternary phase diagram were identified and analyzed (see Table 1).…”

“…48 The most exciting compound, Cu 2 OSeO 3 , with a B20 chiral magnetic oxide, exhibited a unique magnetic skyrmion spin. 8,30,37 CuCl 2 was the first reported nonchalcogen in the multiferroic family, where the Cu 2+ spin spiral invoked spin-induced robust multiferroicity at T N = 24 K, even under the significant effect of quantum fluctuation. 24 Furthermore, multiferroicity was reported in oxyhalide Cu 2 OCl 2 compounds near the liquid nitrogen temperature, 31 where two possible mechanisms, namely spininduced or charge-transfer-induced multiferroicity, were proposed.…”

“…12,25 A lowdimensional crystal structure with anisotropic spin-induced multiferroicity was reported in the magnetic layers of a Cu 3 Bi(-SeO 3 ) 2 O 2 Cl 2 system. 26 In this context, compounds from the CuO-CuCl 2 -SeO 2 ternary phase diagram have been reported to exhibit exotic quantum magnetic states such as skyrmions, along with unique multiferroic properties, 8,24,[27][28][29][30][31][32][33][34][35][36][37][38] as shown in Table 1.…”

Magnonic Metamaterials for Spin-Wave Control with Inhomogeneous Dzyaloshinskii–Moriya Interactions

“…The excitation of short-wavelength propagating spin waves with a wavelength of 45 nm in a YIG thin film covered by Co Fe nanowires was reported in a recent experiment [ 82 ], where the effective damping was only enhanced to about 10 . Recent progress in materials science has proven that certain magnetic insulators do possess sizable DMIs either in their bulk [ 83 , 84 , 85 ] or at the interface [ 86 , 87 , 88 ]. Although these values remain small (typically mJ/m ), these results open interesting perspectives for the achievement of large DMIs in magnetic insulators.…”

In situ control of the helical and skyrmion phases in Cu2OSeO3 using high-pressure helium gas up to 5 kbar

“…Thus, in general, claims of hydrostatic pressure-induced modifications of the topological magnetic properties and phase diagram must be considered very carefully if the sample is pressurized using a standard liquid PTM. This is particularly the case when there are no supporting data obtained by a microscopic probe such as neutron or resonant x-ray scattering which can provide direct indications for the existence of directional strain effects on the magnetism inside the sample [55].…”