Resonance oscillations of magnetic domain walls and bloch lines observed by stroboscopic electron microscopy

Abstract

Forced and free oscillations of magnetic domain walls and Bloch lines are excited in Nio.83Feo.i7 films a t 0.1 to 31 MHz by high frequency magnetic fields and visualized b y stroboscopic electron microscopy (time resolution 1 ns). Resonance of single and coupled oscillators, 'subharmonics', and Bloch line+ross-tie annihilation are directly observed. Specific mass and relaxation time are determined, being m = 2.6 X kg/m, TBL M 15 ns for a Bloch line. Erzwungene und freie Schwingungen von magnetischen Bereichswanden und Blochlinien werden in Nio,saFeo,17 Schichten im Bereich 0,l bis 31 MHz durch hochfrequente Magnetfelder angeregt und durch stroboskopische Elektronenmilrtoskopie abgebildet (zeitliche Auflosung 1 ns). Resonanzen von Einzel-und gekoppelten Schwingern, sowie Blochlinien-Stachel-Vernichtung werden direkt beobachtet. Spezifische Masse und Relaxationszeit werden bestimmt. Sie betragen m = = 2,6 X lo-' kg/m2, z = 30 ns fur eine 9O0-NBel-Wand sowie m B L z kg/m, -CBL M 15 11s fur eine Blochlinie. kg/m2, T = 30 ns for a 90O-NBel wall and mBL z

Quantifying transient states in materials with the dynamic transmission electron microscope

“…The methods generally fall into two approaches, stroboscopic and single shot. The stroboscopic method [5][6][7][8][9][10][11] has been advanced recently in the lab of Prof. A. Zewail at CalTech [12]. In the recent stroboscopic approach [13,14], the specimen is repetitively pumped into a cyclic state by one branch of a femtosecond laser pulsed at a high frequency (MHz or faster) while another branch is used to create a pulse train of electrons that probes the specimen at some particular point in its pump cycle.…”

Nanoscale Mapping of Ultrafast Magnetization Dynamics with Femtosecond Lorentz Microscopy

“…Time-resolved Lorentz microscopy was previously demonstrated for investigations of field-assisted or laser-excited domain wall movement [27][28][29] . Bostanjoglo and coworkers achieved nanosecond temporal resolution by electronically chopping the electron illumination beam 27 .…”

“…Time-resolved Lorentz microscopy was previously demonstrated for investigations of field-assisted or laser-excited domain wall movement [27][28][29] . Bostanjoglo and coworkers achieved nanosecond temporal resolution by electronically chopping the electron illumination beam 27 . Obtaining shorter electron pulses became readily accessible with the advent of laser-triggered electron sources [30][31][32] , extending Lorentz microscopy into the nanosecond 28 and picosecond 29 regime.…”

Few-nm tracking of current-driven magnetic vortex orbits using ultrafast Lorentz microscopy

“…Importantly, the versatile in-situ environment of TEM enables the observation of nanoscale magnetic changes with optical [11,30,31] or electrical stimuli [32][33][34]. Time-resolved transmission electron microscopy [35][36][37] has in some instances been used to address magnetization dynamics [38][39][40][41]. The recent advance of highly coherent photoelectron sources [42,43] promises substantially enhanced contrast and resolution in ultrafast magnetic imaging [44], but has, to date, not been combined with synchronized electrical stimuli.…”