Unoccupied electronic states of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">Fe</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>4</mml:mn></mml:msub></mm

We present an experimental study that offers first insights into the unoccupied electronic states of a pristine <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mrow><a:mo>(</a:mo><a:msqrt><a:mn>2</a:mn></a:msqrt><a:mo>×</a:mo><a:msqrt><a:mn>2</a:mn></a:msqrt><a:mo>)</a:mo></a:mrow><a:mtext>R</a:mtext><a:mn>45</a:mn><a:msup><a:mspace width="0.16em"/><a:mo>∘</a:mo></a:msup></a:mrow></a:math> reconstructed <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:msub><c:mi>Fe</c:mi><c:mn>3</c:mn></c:msub><c:msub><c:mi mathvariant="normal">O</c:mi><c:mn>4</c:mn></c:msub></c:mrow></c:math>(100) surface. We initially demonstrate the successful sample preparation by analyzing the surface periodicity and chemical composition by low-energy electron diffraction and Auger electron spectroscopy, respectively. Using angle-resolved inverse photoemission, we study the unoccupied electronic states. We observe three nondispersive emissions, one dominant feature around <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mn>2</e:mn><e:mspace width="0.16em"/><e:mi>eV</e:mi></e:mrow></e:math> above the Fermi level and two additional ones at higher energies. For the low-lying triple-split feature, we propose two possible interpretations based on former theoretical studies. We either ascribe it to <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mn>3</g:mn><g:mi>d</g:mi></g:math>-related bandgroups originating from tetrahedrally and octahedrally coordinated bulk iron atoms or attribute it to a mixture of <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mn>3</h:mn><h:mi>d</h:mi></h:math> states originating from octahedrally coordinated iron atoms within the bulk and the reconstructed surface layer. The high-lying features are ascribed to bulk bands based on the experimentally observed characteristics.