2021/06/02 by D. Velázquez Rodriguez, D Velázquez Rodriguez, J. Gómez +9
Physics and Astronomy · #Magnetic properties of thin films #Quantum and electron transport phenomena #Physics of Superconductivity and Magnetism
paper · doi:10.1088/1361-6463/ac02fc
Abstract We have investigated the spin pumping phenomenon in Fe 80 Co 20 /Ta bilayers of different thicknesses in which the ferromagnet grows epitaxially on MgO substrates. We have obtained a Gilbert damping constant for Fe 80 Co 20 as low as α = 1.3(1) × 10 −3 , which is smaller than values generally reported in metallic ferromagnets. From the dependence of α with the Fe 80 Co 20 thickness, we extracted the value of the effective spin mixing conductance <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msup> <mml:mi>g</mml:mi> <mml:mrow> <mml:msup> <mml:mi/> <mml:mrow> <mml:mo stretchy="false">↑↓</mml:mo> </mml:mrow> </mml:msup> </mml:mrow> </mml:msup> </mml:math> = 5.7(3) × 10 14 cm −2 . Analyzing the Ta and Fe 80 Co 20 thickness dependence of the inverse spin Hall effect voltage, we obtained the transport parameters <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi>λ</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext>sd</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> </mml:math> = 1.1(3) nm and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mi mathvariant="normal">Θ</mml:mi> <mml:mrow> <mml:mrow> <mml:mtext>SH</mml:mtext> </mml:mrow> </mml:mrow> </mml:msub> </mml:math> = –0.024(3). We have developed an expression to quantify the efficiency of the spin pumping phenomenon in ferromagnetic/nonmagnetic metal bilayers. The calculated efficiency shows that the Fe 80 Co 20 /Ta system is up to an order of magnitude more efficient than other metallic ferromagnetic bilayers reported in the literature.