Wednesday 21 January 2015, 2.00PM
Speaker(s): Professor Gerrit van der Laan, Magnetic Spectroscopy Group, Diamond Light Source, Didcot, Oxfordshire
Improved understanding of precessional magnetization dynamics is essential for the continued development of high frequency magnetic devices such as hard disk drives and spin oscillators. In the past, conventional ferromagnetic resonance (FMR) has been used extensively to determine fundamental parameters that affect magnetism in thin films using resonance frequencies (related to internal and applied fields) and relaxation (determined by damping of the resonance). However, the growing complexity of many modern ferromagnetic materials and devices requires the development of measurement techniques that reveal in a more direct fashion the microscopic origin of relevant interactions.
Recently, x-ray detected FMR (XFMR) has emerged as a powerful synchrotron radiation based tool that can be used to study the element-selective magnetization dynamics. Magnetic and chemical contrast in XFMR is obtained by x-ray magnetic circular dichroism (XMCD), while the phase difference of the magnetization precessions is monitored using a stroboscopic measurement technique. A unique property of time-resolved XFMR is the visualisation of the magnetization precession of each individual layer in a magnetic device. Examples are shown where the measured amplitude and phase response of the magnetic layers provide a clear signature of spin transfer torque (STT) coupling due to spin pumping.
Location: P/X/001 Physics/Electronics Lecture Theatre