Abstract
It is generally accepted that Bi2Te3 prepared from stoichiometric melts has p-type charge carriers generated from BiTe-type antisite defects, while Bi2Te3 grown under Te-rich condition becomes n-type due to another type of TeBi antisite defects. We report the magnetic and transport properties of GdxBi2-xTe3 prepared from stoichiometric melts, where p-type charge carriers are dominant. The physical properties of all the samples have no significant changes with varying the nominal Gd composition up to x = 0.2. Compared with n-type GdxBi2-xTe3 samples grown under Te-rich condition, we find low solubility for all the samples and no clear signature of antiferromagnetic order. These results suggest that the Gd doping rate in GdxBi2-xTe3 is governed by the type of antisite defects and charge carriers, so that the antiferromagnetic ordering is not eventually introduced.
Highlights
Topological insulators (TIs) have attracted a lot of interest in condensed matter physics and material science due to their gapless surface states exhibiting various quantum phenomena applicable for spintronics and quantum computation devices.[1,2,3] By introducing magnetic order intoTIs, different kinds of quantum phenomena can be achieved such as quantum anomalous Hall effect, image magnetic monopoles, and giant magneto optical effects.[4,5,6,7,8] The simplest way to introduce the magnetic order into TIs is doping of magnetic impurities, as demonstrated in dilute magnetic semiconductors (DMSs).[9]
We have reported that antiferromagnetic order is induced by 4f rare-earth elements such as Ce and Gd in both Bi2Se3 and Bi2Te3.16–18 In theory, the antiferromagnetic order can coexist with topological surface states when it is type-II antiferromagnetic,[19,20,21] while the topological insulating state can be changed to trivial antiferromagnetic state due to large Coulomb repulsion.[22]
The equilibrium solubility of Gd in bulk samples varies from 0.01 to 0.20 with the growth method,[9,16] whereas the solubility of thin-film samples synthesized by non-equilibrium method such as molecular beam epitaxy reaches up to 0.80.23,24 In our previous studies, we reported a magnetic transition from paramagnetic to antiferromagnetic phase at x = 0.09 in Te-excessive GdxBi2-xTe3 system,[16] with n-type charge carriers due to TeBi-type antisite defects generated in Te-rich growth condition
Summary
Topological insulators (TIs) have attracted a lot of interest in condensed matter physics and material science due to their gapless surface states exhibiting various quantum phenomena applicable for spintronics and quantum computation devices.[1,2,3] By introducing magnetic order into. In a form of GdxBi2-xTe3, there have been a wide variety of Gd solubility limits.[9,16,23,24] The equilibrium solubility of Gd in bulk samples varies from 0.01 to 0.20 with the growth method,[9,16] whereas the solubility of thin-film samples synthesized by non-equilibrium method such as molecular beam epitaxy reaches up to 0.80.23,24 In our previous studies, we reported a magnetic transition from paramagnetic to antiferromagnetic phase at x = 0.09 in Te-excessive GdxBi2-xTe3 system,[16] with n-type charge carriers due to TeBi-type antisite defects generated in Te-rich growth condition. One may expect in p-type GdxBi2-xTe3 that two different types of charge carriers are competing since the Dirac point of topological surface states is buried in bulk band gap. The excessive Gd is detected as secondary phases such as Gd2O3, GdTe2, and GdTe3
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