Large scale arrays of Co/Pd and Fe60Al40 nanomagnets with tunable magnetic properties for recording and magnonic applications

The fabrication and characterization of nanopatterned magnetic thin films is an important topic for magnetic recording media, sensors, information processing, and magnonic crystals. This broad spectrum of applications results from the possibility of controlling the magnetic properties of such systems in wide range by introducing artificial defects to ferromagnetic material and arranged them in ordered or disordered arrays.
This presentation will focus on the magnetic properties and switching behaviour of magnetic Co(0,3 nm)/Pd(0,9 nm) and Fe60Al40 (40 nm) films composed of arrays of dots, antidots and triangles. Such arrays of nanostructures were created by colloidal lithography complemented by RF-plasma etching and ion irradiation with 20 keV Ne+ ions, which resulted in nanomagnets with sizes down to 30 nm [1].
Using SQUID magnetometry, changes in coercive field, saturation magnetization, loop squareness, and magnetic anisotropy constant have been determined in a temperature range of 5 K – 350 K and compared with non-patterned films. The domain shapes and sizes together with the switching behaviour were studied by scanning magnetoresistive microscopy utilizing commercial reading-writing head from HDD. We have shown that the coercivity reach a maximum values for the arrays with a separation length between nanomagnets close to the domain wall width, which is caused by strong domain wall pinning. The impact of the patterning on the magnetic anisotropy is also clearly seen. The observed influence of surface morphology on magnetic properties and magnetization switching characteristics was confirmed by the micromagnetic modelling using mumax3 software. The results demonstrated that the proposed approach can be effectively used to produce large scale magnetic arrays with properties widely tuneable by temperature and patterning period.

This work was supported by Polish National Science Centre grant No 2017/01/X/ST8/01409.