11:15 AM - 11:30 AM
▼ [6a-C18-10] Spin precession control in ferromagnetic thin films by two-pulse excitation measurement
Keywords:Spin dynamics, Magneto-optical Kerr effect, Ultrafast optical spectroscopy
In the opto-magnetism, ultrafast-laser-induced coherent control of the spin precession motion in magnetic materials has gotten a lot of attention and has been studied extensively. To date, two types of the spin precession excitation methods by the thermal and non-thermal excitation with an ultrafast pulse laser were proposed. The coherent control of the spin precession motion was achieved by the non-thermal excitation such as the inverse Faraday effect and direct THz magnetic field excitation. In these studies, using the two-pulse excitation, suppression and enhancement of the spin precession were achieved by changing the relative time delay between the two pump pulses. Although it is known that the spin precession motion is easily driven through the thermal excitation by the laser heating, the control of spin precession via a thermal excitation has not been observed. In this work, we explore the possibility of spin precession control in permalloy thin film samples by the laser heating.
In this work, permalloy thin films with a thickness of 20 nm were used as a sample. In our optical setup, we used Ti:Sapphire laser pulses with a wavelength of 800 nm, a pulse width of 90 fs, and a repetition rate of 80 MHz as a light source. The laser pulses were divided in three pulses. Two of them were used for the double pump pulses with a relative time delay. The wavelength of pump pulses were converted from 800 to 400 nm using a BBO crystal. The other laser pulse was used as a probe pulses for the detection of the spin precession motion with the magneto-optical Kerr effect. A magnetic field of a several hundreds of mT with a field angle of ~15 degrees tilted from the normal of the sample plane was applied to the sample. By changing the relative delay time between the two pump pulses, we observed that the amplitude of the spin precession motion was suppressed or enhanced. This means that we could control the spin dynamics in permalloy thin films by the double pump pulses. In this presentation, we will discuss the experimental results in detail.
In this work, permalloy thin films with a thickness of 20 nm were used as a sample. In our optical setup, we used Ti:Sapphire laser pulses with a wavelength of 800 nm, a pulse width of 90 fs, and a repetition rate of 80 MHz as a light source. The laser pulses were divided in three pulses. Two of them were used for the double pump pulses with a relative time delay. The wavelength of pump pulses were converted from 800 to 400 nm using a BBO crystal. The other laser pulse was used as a probe pulses for the detection of the spin precession motion with the magneto-optical Kerr effect. A magnetic field of a several hundreds of mT with a field angle of ~15 degrees tilted from the normal of the sample plane was applied to the sample. By changing the relative delay time between the two pump pulses, we observed that the amplitude of the spin precession motion was suppressed or enhanced. This means that we could control the spin dynamics in permalloy thin films by the double pump pulses. In this presentation, we will discuss the experimental results in detail.