Making a reconfigurable artificial crystal by ordering bistable magnetic nanowires

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Spin-wave excitations, known as magnons, are fundamental to understanding magnetic phenomena.
• One-dimensional (1D) magnonic crystals offer unique platforms for controlling spin-wave propagation.
• Nickel-iron (Ni80Fe20) alloys are widely used in spintronic devices due to their magnetic properties.

Purpose of the Study:

• To investigate the spin-wave (magnon) band structures in a 1D magnonic crystal composed of Ni80Fe20 nanowires.
• To analyze the influence of magnetic ordering (parallel vs. antiparallel) between neighboring nanowires on magnon dispersion.
• To explore the tunability of the magnonic band gap by an external in-plane magnetic field.

Main Methods:

• Fabrication of a 1D magnonic crystal using Ni80Fe20 nanowires.
• Experimental investigation of spin-wave excitations.
• Analysis of magnon band structures under varying magnetic field conditions.

Main Results:

• Two distinct magnon band structures were observed, corresponding to parallel and antiparallel magnetic alignments of adjacent nanowires.
• At zero magnetic field, the antiparallel alignment modes approximated zone-folding of the parallel case.
• A non-zero in-plane magnetic field opened a forbidden frequency gap at the Brillouin zone boundary, with the 1D stop band gap scaling with the applied field.

Conclusions:

• The magnetic ordering of nanowires in a 1D magnonic crystal significantly dictates the magnon band structure.
• External magnetic fields provide a mechanism to tune the magnonic band gap, creating a periodic potential for Bragg reflection of magnons.
• This tunability offers potential for developing novel magnonic devices and controlling spin-wave propagation.