Magnetic Transition Induced By Isostructural Alloying Under The Heusler Structure

Heusler alloys contain diverse physical properties and great application prospects.Heusler alloys tend to exhibit novel properties in the transition from ferromagnetic to antiferromagnetic,which have great potential applications in spintronics.The main work of this paper is to use the transition from ferromagnetism to antiferromagnetism as the entry point under the Heusler structure,and induce magnetic transition to synthesize new materials by the method of isostructural alloying,and then explore the physical properties and functional characteristics of new materials during the transformation process.This paper focuses on the Co-Ru-based Heusler alloys,and the main research results are summarized as follows:The Co_2-xRu_xMn Si(x=0-2)series alloys were designed and synthesized by the method of isostructural alloying.Combined with theoretical and experimental results,we found that with the increase of Ru doping amount x,the lattice constant increases,while the magnetic moment decreases,and there was a transition from ferromagnetism to antiferromagnetism.It is found that the Co_2-xRu_xMn Si(x=0,0.25)alloys are rigorous half-metallic and show a T³dependence of resistance at low temperature.The Co_2-xRu_xMn Si(x=0.5,0.75,1)alloys are the nearly half-metallic materials and show a semiconductive dependence of resistance at low temperature.When the Ru doping content x>1,this series alloys begin to undergo a transition from ferromagnetism to antiferromagnetism.The Co_2-xRu_xMn Ge(x=0-2)alloys with bcc single-phase structure were synthesized by arc smelting-quenching.Combined with theoretical and experimental datas,we found that the lattice constant increases with the Ru content x increases.When the Ru content x increase from 0 to 1,the magnetic moment decreases linearly.The Co_2-xRu_xMn Ge series alloys exhibit ferromagnetism,have low coercivity and excellent soft magnetic properties.When the Ru content x>1,antiferromagnetic coupling begins to occur in these alloys,and antiferromagnetic coupling gradually increases until the Ru content x=2,namely Ru₂Mn Ge,it is transformed into antiferromagnetism.The martensitic transformation behavior is observed in a certain range of Ru-rich alloys,and a series of new magnetic shape memory alloys are found.The Co_2-xRu_xFe Si(x=0-2)alloys were synthesized by arc melting.It is found thatthe lattice constant of the Co_2-xRu_xFe Si(x=0-2)alloys increases monotonically with the increase of Ru content x.The alloys with Ru content x=0-0.8 exhibit a highly ordered L2₁structure,while the Ru content x>0.8,the superlattice diffraction peak(111)disappear and transform into B2 structure.When the Ru content x>0.8,the saturation magnetization deviated from the trend of the Slater-Pauling curve,and antiferromagnetic coupling begins to appear in the internal magnetic structure of the alloys.It is speculated that the ferromagnetism to antiferromagnetisem transition in this series of alloys is caused by the decrease of atomic order in the crystal.In addition,obvious thermal hysteresis is observed in the M-T curves of the partially rich-Ru alloys,which indicate that the series of alloys have thermoelastic martensitic transformation behavior within a certain range of composition.