Mid-infrared element-specific selective manipulation of the ultrafast magneto-optical Kerr effect dynamics in the ferrimagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>FeCr</mml:mi> <mml:mn>2</mml:mn> </m

<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi>FeCr</a:mi> <a:mn>2</a:mn> </a:msub> <a:msub> <a:mi mathvariant="normal">S</a:mi> <a:mn>4</a:mn> </a:msub> </a:mrow> </a:math> is a ferrimagnet with two oppositely ordered spin sublattices (Fe and Cr), connected via superexchange interaction, giving a nonzero net magnetic moment. We show, using time-resolved measurements of the magneto-optic Kerr effect, how the magnetic dynamics of the sublattices can be selectively manipulated by resonantly perturbing the Fe sublattice with ultrashort laser pulses. The mid-infrared excitation through intra-atomic Fe <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:mi>d</c:mi> <c:mtext>−</c:mtext> <c:mi>d</c:mi> </c:mrow> </c:math> transitions triggers markedly slower dynamics in comparison to an off-resonant pumping affecting both of the two sublattices simultaneously. By changing probe wavelength to move in and out of resonance with the Fe <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mrow> <d:mi>d</d:mi> <d:mtext>−</d:mtext> <d:mi>d</d:mi> </d:mrow> </d:math> transitions, we also show the specific contributions of the Fe sublattice to these dynamics.