Ferrimagnetic Tb/Co multilayers patterned by ion bombardment as substrates for magnetophoresis

Area of Science:

• Materials Science
• Nanotechnology
• Biophysics

Background:

• Perpendicular magnetic anisotropy (PMA) materials are crucial for magnetic storage and spintronic devices.
• Localized modification of magnetic properties can create complex magnetic field landscapes.
• Controlling microscale objects using magnetic fields is a key challenge in microfluidics and lab-on-a-chip systems.

Purpose of the Study:

• To investigate the magnetic field generation capabilities of ion beam-modified ferrimagnetic multilayers.
• To demonstrate the controlled manipulation of superparamagnetic beads using these engineered magnetic fields.
• To explore the potential of this system for microscale transport applications.

Main Methods:

• Fabrication of Tb/Co based ferrimagnetic multilayers.
• Focused ion beam (FIB) irradiation with 30 keV Ga+ ions to locally alter magnetic properties.
• Observation of superparamagnetic bead movement in aqueous suspension over the patterned magnetic structures.
• Application of time-varying external magnetic fields to control bead dynamics.

Main Results:

• Ion bombardment induced significant local changes in effective magnetization, creating high magnetic field gradients.
• Superparamagnetic beads responded to the magnetostatic energy landscape generated by the patterned magnetic structure.
• Controlled propulsion of beads was achieved using external magnetic fields, reaching velocities up to 40 µm/s at 10 Hz.
• The bead motion was tunable by adjusting the external field parameters.

Conclusions:

• Focused ion beam irradiation is an effective method for patterning magnetic multilayers to create controllable magnetic landscapes.
• The engineered magnetic fields can precisely manipulate superparamagnetic beads in microfluidic environments.
• This technique shows promise for developing novel lab-on-a-chip devices for sensing and manipulation applications.