Tuning the room temperature ferromagnetism in Fe <sub>5</sub> GeTe <sub>2</sub> by arsenic substitution
Andrew F May, Jiaqiang Yan, Raphael Hermann, Mao-Hua Du, Michael A McGuire
Abstract
Abstract In order to tune the magnetic properties of the cleavable high-Curie temperature ferromagnet Fe <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi/> <mml:mrow> <mml:mn>5</mml:mn> <mml:mo>−</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:math> GeTe 2 , the effect of increasing the electron count through arsenic substitution has been investigated. Small additions of arsenic (2.5% and 5%) seemingly enhance ferromagnetic order in polycrystalline samples by quenching fluctuations on one of the three magnetic sublattices, whereas larger As concentrations decrease the ferromagnetic Curie temperature ( T C ) and saturation magnetization. This work also describes the growth and characterization of Fe 4.8 AsTe 2 single crystals that are structurally analogous to Fe <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi/> <mml:mrow> <mml:mn>5</mml:mn> <mml:mo>−</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:math> GeTe 2 but with some phase stability complications. Magnetization measurements reveal dominant antiferromagnetic behavior in Fe 4.8 AsTe 2 with a Néel temperature of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>T</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext>N</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> </mml:math> 42 K. A field-induced spin-flop below T N results in a switch from negative to positive magnetoresistance, with significant hysteresis causing butterfly-shaped resistance loops. In addition to reporting the properties of Fe 4.8 AsTe 2 , this work shows the importance of manipulating the individual magnetic sublattices in Fe <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi/> <mml:mrow> <mml:mn>5</mml:mn> <mml:mo>−</mml:mo> <mml:mi>x</mml:mi> </mml:mrow> </mml:msub> </mml:math> GeTe 2 and motivates further efforts to control the magnetic properties in related materials by fine tuning of the Fermi energy or crystal chemistry.