Spatially resolved GHz magnetization dynamics of a magnetite nano-particle chain inside a magnetotactic bacterium

Thomas Feggeler,Heiko Wende,Katharina J Ollefs,Ralf Meckenstock,Michael Winklhofer,Michael Farle,Hendrik Ohldag,Detlef Spoddig,Benjamin W Zingsem

doi:10.1103/physrevresearch.3.033036

Abstract

Understanding magnonic properties of nonperiodic magnetic nanostructures requires real-space imaging of ferromagnetic resonance modes with spatial resolution well below the optical diffraction limit and sampling rates in the 5--100 GHz range. Here, we demonstrate element-specific scanning transmission x-ray microscopy-detected ferromagnetic resonance (STXM-FMR) applied to a chain of dipolarly coupled ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$ nano-particles (40--50 nm particle size) inside a single cell of a magnetotactic bacterium Magnetospirillum magnetotacticum. The ferromagnetic resonance mode of the nano-particle chain driven at 6.748 GHz and probed with 50 nm x-ray focus size was found to have a uniform phase response but non-uniform amplitude response along the chain segments due to the superposition of dipolar coupled modes of chain segments and individual particles, in agreement with micromagnetic simulations.

Highlights

Magnonics deals with the controlled excitation and detection of spin waves in magnetic media [1,2,3,4,5,6,7]
Faster dynamical processes can be studied with pump-probe schemes repeated for a sequence of delay times with each repetition starting from the same initial state and accumulating many pump-probe pulse cycles in a stroboscopic procedure
Pump-probe schemes are used in time-resolved photoemission electron microscopy [11,12] and ultrafast transmission electron microscopes [13,14] capable of probing transient demagnetization dynamics of nanodiscs with sub-100 nm resolution and subpicosecond delay time resolution [15]

Summary

Introduction

Magnonics deals with the controlled excitation and detection of spin waves in magnetic media [1,2,3,4,5,6,7]. Resolved GHz magnetization dynamics of a magnetite nano-particle chain inside a magnetotactic bacterium We demonstrate element-specific scanning transmission x-ray microscopydetected ferromagnetic resonance (STXM-FMR) applied to a chain of dipolarly coupled Fe3O4 nano-particles (40–50 nm particle size) inside a single cell of a magnetotactic bacterium Magnetospirillum magnetotacticum.

Results

Conclusion