Influence Of Doping Elements On Phase Transition And Magnetic Properties Of MnNiIn Based Alloys

Mn-Ni-In based alloys are a kind of newly developed magnetic controlled functional material.Because of the strong magneto-structural coupling in these alloys,significant magnetocaloric effect can be realized under the external magnetic field.Thus,Mn-Ni-In alloys can be conceived as potential candidate materials for the magnetic refrigeration application.However,the phase transformation hysteresis of the alloys is large and leads to a large hysteresis loss,which is not conducive to greater effective cooling capacity.Therefore,how to reduce the phase transformation hysteresis is of great significance to the application of the alloy.In addition,it is of great importance for magnetic refrigerants to have a large magnetocaloric effect in a wide temperature range.In this paper,Mn-Ni-In based alloys with the nominal composition of Mn50-xNi37Co4In9Cux(x=0,1,2,3,4)and Mn50Ni38In9-xCo3Snx(x=1,2,3,4)were prepared byarcmeltingprocessinargonatmosphere.The effect of composition on the martensitic transformation,the crystal structure,the microstructure and the magnetocaloric properties were systematically studied,which is expected to offer some guidelines for the further composition design and property improvement.For Mn50-xNi37Co4In9Cux(x=0,1,2,3,4)alloys,with the increase of Cu content,the electron concentration and the martensitic transformation temperature gradually increased,but the hysteres is decreased.When the content of Cu is 0%-1%,the room temperature phase of the alloys is austenite phase,and the room temperature phase is martensitic phase when the Cu content is 2%-4%;as the atomic radius of Cu is smaller than the atomic radius of Mn,the cell volume will decrease with the increase of the Cu content.Mn50-xNi37Co4In9Cux(x=0,1,2,3,4)alloyshave magnetic structure coupling characteristics.The magnetic field can induce reverse martensitic transformation.And the phase transition is accompanied by significant magnetocaloric effect.The maximum magnetic entropy change value of Mn46Ni37Co4In9Cu4 in 3 T magnetic fieldis 15.8 Jkg-1K-1.The maximum effective refrigeration capacity of the alloys is 122.1 Jkg-1,and the maximum thermal adiabatic temperature change of the alloy under the 1.5 T magnetic field is 0.89 K.For Mn50Ni38In9-xCo3Snx(x=1,2,3,4)alloys,the martensitic transformation temperature and the hysteres is decreased gradually with the increase of Sn content.When the content of Sn is 1%-2%,the room temperature phase of the alloys is martensitic phase,and the room temperature phase is austenite phase when the Sn content is 3%-4%;as the atomic radius of Sn is smaller than the atomic radius of In,the cell volume will decrease with the increase of the Sn content.Mn50Ni38In9-xCo3Snx(x=1,2,3,4)alloys have magnetic structure coupling characteristics.The magnetic field can induce reverse martensitic transformation.And the phase transition is accompanied by significant magnetocaloric effect.The maximum magnetic entropy change value is 13.1 Jkg-1K-1in 3 T magnetic field.The maximum effective refrigeration capacity of the alloys is 77.5 Jkg-1,and the maximum thermal adiabatic temperature change of the Mn50Ni38In6Co3 Sn3alloy under the 1.5 T magnetic field is 1.25 K.