Book of abstracts - Euro-MBE 2011 - CNRS

Mo2.1
MBE growth of LiMnAs
Vít Novák
Institute of Physics of the Academy of Sciences, Cukrovarnická 10, 162 53 Praha, Czech Republic
Compound semiconductors derived from silicon have had a tremendous impact on the physics and
applications of semiconductors. Two textbook examples are the direct gap III-V semiconductors and
the prototype magnetic II-VI semiconductors, Fig.1. Remarkably, none of the other closest relatives of
silicon from the I-III-IV and I-II-V compounds have so far been synthesized by modern epitaxial
growth techniques and the potential of these compounds has remained virtually unexplored. In this
talk we focus on I-Mn-V compounds which surprisingly have not previously been considered as
candidate semiconductors. One of the key motivations to establish their semiconducting electronic
structure is that they are among the rare known silicon relatives with magnetic ordering temperature
safely above room temperature.
Fig.1: Closest relatives of silicon emerging by applying the “proton transfer” rule.
We demonstrate on LiMnAs that high-quality materials with group-I alkali metals in the crystal structure
can be grown by standard solid source molecular beam epitaxy [1]. The epitaxial LiMnAs film exhibits
optical gap, evidenced by optical transmission measurements and consistent with the band structure
obtained by our ab initio calculations. Squid magnetometry measurements support earlier reports of
high antiferromagnetic ordering temperature.
We propose a strategy for employing I-Mn-V compounds in high-temperature semiconductor
magneto-electronics. The key principle is to utilize relativistic magnetic and magneto-transport anisotropy
effects whose common characteristics is that they are an even function of the microscopic magnetic
moment vector and are therefore in principle equally well present in materials with ferromagnetic (FM) and
antiferromagnetic (AFM) order. The application of AFM semiconductors to exchange bias FMs opens an
immediate research opportunity for integrating conventional semiconductor micro and opto-electronics
functionalities directly in the exchange-biasing AFM layers in common magneto-electronic devices. In
these structures LiMnAs can be combined, e.g., with lattice matched FM semiconductor (In,Mn)As or
conventional transition metal FMs. The FM-AFM coupling can also be used for controlling the staggered
moment orientation in the AFM by the exchange spring effect induced by rotating moments in the
ferromagnet.
[1] T. Jungwirth, et al., Phys. Rev. B 83, 035321 (2011).
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* Contact: vit.novak@fzu.cz