8:40 AM - NM03.06.04
Carrier Conduction and Magnetic Interactions in a Nanostructured Epitaxial Ferromagnet/Semiconductor Fe: FeVSb
Estiaque Haidar Shourov1,Chenyu Zhang1,Paul Voyles1,Jason Kawasaki1
University of Wisconsin–Madison1
Magnetic semiconductors are attractive for memory devices and spintronic applications . However, the practical utility of dilute magnetic semiconductors (DMS) such as Mn: GaAs, albeit having all key ingredients for these applications, are hindered due to low Curie temperature. On the other hand, narrow bandgap semiconductors often make excellent thermoelectric candidates. A conventional strategy for improving the thermoelectric figure of merit (ZT) is to decrease the phonon thermal conductivity via nano-structuring . Recently, it has been suggested that magnon drag (spin wave) , spin fluctuations , and enhanced effective mass  are alternative strategies to enhance thermoelectric performance by enhancing the power factor. Here we demonstrate the controllable synthesis of a ferromagnet/semiconductor nanostructured system: Fe nanoparticles embedded epitaxially within a semiconducting FeVSb matrix. Transmission electron microscopy confirms that the nanoparticle formation is mediated by bulk segregation for all composition greater than 10% excess Fe in stoichiometric FeVSb. Our Fe: FeVSb thin films, grown by molecular beam epitaxy, display magnetic moment and anomalous Hall effect that scale with the volume fraction of Fe nanoparticles. The parent stoichiometric FeVSb is predicted to be diamagnetic, but our stoichiometric films also exhibits magnetic signatures in transport and magnetometry at 300K. This suggests that within the solubility limit of Fe, Fe1+δVSb, where δ is the bound of solubility, is a potential dilute magnetic semiconductor with Curie temperature greater than room temperature. Additionally, the ferromagnetic nanoparticles can induce spin polarized charge carriers in the semiconducting matrix due to proximity effect, making this highly controllable and tunable system appealing for spintronics. Our angle-resolved photoemission spectroscopy (ARPES) measurements on the parent semiconductor FeVSb reveal an enhanced effective mass due to electronic correlations . The combination of nanostructure precipitates, magnetic interaction, and electronic correlation in this highly tunable heterostructure presented here offers a promising route for new thermoelectric application for practical waste heat recovery.
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