Synthesis and characterization of a percolating, ferromagnetic, Mn-rich Ge:Mn nanonet with hysteretic transport properties

The coupling of the magnetization state with the electrical transport properties of a magnetic semiconductor is one big step to new spintronics devices. The coupling can be proved by SQUID magnetization and Hall resistance measurements. In a previous work we fabricated ferromagnetic Ge:Mn by Mn ion implantation and pulsed laser annealing (PLA) and observed a clear hysteretic Hall resistance correlated with the magnetization below 10 K [1]. Recently, by applying optimized PLA conditions, we fabricated a percolating, Mn-rich Ge:Mn nanonet with hysteretic Hall resistance up to 30 K [2]. This nanonet is embedded in crystalline Ge:Mn between 5 nm and 40 nm under the sample surface. The reason for the formation of the nanonet is a constitutional undercooling of the liquid Ge-Mn-alloy during the recrystallization process using a relatively long pulse length of 300 ns which helped to imprint an optimal temperature profile during PLA [3]. We applied etching to confirm the contribution of the nanonet to the electrical transport properties. In the future such nanonets may be used to spin-polarize free charge carriers in magnetic semiconductors at room temperature. Because the nanonet can be selectively etched, substrates with ordered “nano-channels” can be fabricated which may be also useful in the field of nanoimprint-lithography. [1] S. Zhou et al., Phys. Rev. B 81, 165204 (2010) [2] D. Bürger et al., Appl. Phys. Lett. 100, 012406 (2012) [3] J. Narayan, J. Appl. Phys. 52, 1289 (1981)