Enhancement of magnetic susceptibility of Mn₃Sn single crystal under GPa-level uniaxial stress

Abstract

At room temperature, controlling the spin of noncollinear antiferromagnetic Mn<sub>3</sub>Sn presents a challenge. In this study, we modulate the magnetic structure by subjecting Mn<sub>3</sub>Sn single crystals to GPa-level uniaxial stress using a high-pressure binding deformation approach. Initially, the single crystal is sliced into regular cuboids, then embedded in a stainless steel sleeve, and finally, uniaxial stress is applied along the [01<span style="text-decoration:overline">2</span>0] and [01<span style="text-decoration:overline">1</span>0] directions of the Mn<sub>3</sub>Sn single crystal. Under high stress, the single crystal undergoes plastic deformation. Our observations reveal lattice distortion in the deformed single crystal, with the lattice parameter gradually decreasing as the stress level increases. In addition, the magnetic susceptibility of Mn<sub>3</sub>Sn under GPa uniaxial stress (<i>χ</i>) is different from that under MPa uniaxial stress, and its value is no longer fixed but increases with the increase of stress. When 1.12 GPa stress is applied in [01<span style="text-decoration:overline">2</span>0] direction, <i>χ</i> reaches 0.0203 <i>μ</i><sub>B</sub> f.u.<sup>-1</sup>T<sup>-1</sup>, which is 1.42 times that of the undeformed sample. In the case of stress applied along the [01<span style="text-decoration:overline">1</span>0] direction, <i>χ </i>≈ 0.0332 <i>μ</i><sub>B</sub> f.u.<sup>-1</sup>T<sup>-1</sup> when the stress is 1.11 GPa. This result is also 2.66 times greater than the reported results. We further calculate the trimerization parameter (<i>ξ</i>), isotropic Heisenberg exchange interaction (<i>J</i>), and anisotropic energy (<i>δ</i>) of the system under different stresses. Our results show that <i>ξ</i> gradually increases, <i>J</i> gradually decreases, and <i>δ</i> gradually increases with the increase of stress. These results show that the GPa uniaxial stress introduces anisotropic strain energy into the single crystal, breaking the symmetry of the in-plane hexagon of the kagome lattice, which causes the bond length of the two equilateral triangles composed of Mn atoms to change. Thus, the exchange coupling between Mn atoms in the system is affected, the anisotropy of the system is enhanced, and the antiferromagnetic coupling of the system is enhanced. Therefore, the system <i>χ </i>is no longer a constant value and gradually increases with the increase of stress. This discovery will provide new ideas for anti-ferromagnetic spin regulation.