We perform time-resolved magneto-optical Kerr effect measurements and record the magnetization dynamics for external magnetic fields along various symmetry axes of the chiral magnet MnSi. The different orientations of the magnetic field result in very different magnetization dynamics. For magnetic fields along the $a\text{−}b$ plane, we observe rapid oscillations assigned to magnon modes. These oscillations are detected for various external magnetic fields and are well reproduced by our theoretical spin-wave calculations. When applying magnetic fields at ${45}^{\circ }$ with respect to the $a\text{−}b$ plane and along the $c$ axis, changes in the net magnetization are instead observed. In the absence of external magnetic fields, the net magnetization is zero, and light-induced magnetization is observed. First-principles calculations identify the inverse Faraday effect as the mechanism leading to the observed light-induced magnetization. When sufficiently strong external magnetic fields are applied off the $a\text{−}b$ plane, the MnSi crystal is brought into a ferromagnetic phase, where the laser pulse's demagnetizing effect is observed. This observation suggests that by changing the strength or orientation of the external magnetic field the MnSi crystal can be magnetized or demagnetized using a laser pulse.

Close

PrevNext

View figure in article

• Magnetic coupling
• Magnetization dynamics
• Spin dynamics
• Ultrafast magnetic effects
• Chiral magnets
• Density functional calculations
• Magneto-optical Kerr effect
• Nonlinear optical techniques