Wed, 29 Nov 2017, 10:30 am - 11:30 am
Natural Science Bldg. 312 - Louisville, KY
Doctoral Seminars
Farzaneh Hoveyda
PhD Thesis Defense


Unexpected observation of ultrafast demagnetization and subsequent time-resolved studies on laser-induced magnetization switching opened a new door to both fundamental physics and technological applications. The materials used in applications are often ferromagnetic and AOS has been observed in a large variety of ferromagnetic materials. Realizing that all-optical switching (AOS) of magnetization can be done faster than the precession limit, hints to its potential for applications in increasing the writing speed and shrinking the size of data storage devices and explains the considerable research interest in AOS in ferromagnetic material. However, unlike ferrimagnets, the mechanism of AOS in ferromagnetic materials remains unclear. Thus, it is worthwhile to investigate the role of different accessible parameters in ultrafast laser-induced switching of ferromagnetic materials.

The purpose of this work is to shed light on the responsible factors for AOS in ferromagnetic superlattices. For this purpose, different magnetic samples were deposited. Magnetic properties of the sample were explored using various methods. We used Magneto-optical effect (MOKE and Faraday) and vibrating sample magnetometer (VSM) experiments to measure the hysteresis behavior of the samples and to address the magnetization direction and the magnetic anisotropy. Employing magnetic force microscopy (MFM) and polarizing microscopy, we imaged the magnetic structure of the sample. A femtosecond laser was utilized in a writing setup to explore the parameters that influence obtaining AOS. The time-resolved pump-probe setup was used to detect ultrafast demagnetization in different samples. Moreover, experiments were carried out via pump-probe setup to study heat diffusion in superlattice samples on glass substrates.


Natural Science Bldg. 312