Fabrication and temperature-dependent magnetic properties of large-area L1₀-FePt/Co exchange-spring magnet nanopatterns

Exchange-spring (ES) magnets L1₀-FePt/Co nanopatterns with out-of-plane texture have been fabricated by using nanoimprint lithography (NIL) in combination with inductively coupled plasma reactive etching process. The patterns are regularly arranged 60 nm diameter size nanomagnets, and different thickness of the Co soft magnet layers hysteresis loops of the different ratio of Co soft magnet addition on L1₀-FePt hard nanomagnet was measured by superconducting quantum interference device (SQUID) magnetometry in the temperature range from 50 K to 350 K. The influence of exchange-coupling between hard and soft magnet by thickness control on magnetic properties of these nanocomposite patterns was investigated. The magnetic property results have proved to be possible tuned magnetic properties of magnet nanopatterns. According to exchange-coupling between two-phase quantities, the magnetic properties and magnetization reversal mechanism depend significantly. The exchange-spring magnet nanopatterns have a smaller coercivity, remanence, and magnetic anisotropy, while a higher saturation polarization than pure hard magnet nanopattern due to the soft magnetic layer. The temperature dependence of the coercivity was analyzed by the universal relation within the framework of micromagnetism. The obtained microstructural parameters α and N_eff give evidence for a reduction of the coercivity by the exchange coupling in the exchange-spring magnets.