The influence of substitution of Mn by Fe and Co on magnetocaloric effect and magnetoresistance properties of SmMn2Ge2

Abstract Magnetocaloric and magnetoresistance properties of SmMn2−xFexGe2 (x=0.05 and 0.10) and SmMn2−xCoxGe2 (x=0.05 and 0.15) compounds have been studied by magnetic and resistance measurements in the temperature range between 30 and 350 K. All compounds exhibit metamagnetic transition from antiferromagnetism to ferromagnetism around the Sm moments ferromagnetic ordering temperature-TSm and Mn moments antiferromagnetic ordering temperature-TN1. The magnetic entropy changes of these compounds are estimated from the Maxwell equation, Maxwell Clausius Clapeyron equation, Landau theory and mean-field theory. The maximum magnetic entropy change values of SmMn1.90Fe0.10Ge2 and SmMn1.85Co0.15Ge2 compounds are −8.1 J kg−1 K−1 and −5.1 J kg−1 K−1 in a magnetic field change of 5 T, respectively. These compounds show negative magnetoresistance around the magnetic phase transition temperatures. The magnetoresistance value of SmMn1.95Fe0.05Ge2 is −23% at TSm which is bigger than the magnetoresistance value of SmMn2Ge2 (−15%).