Preparation And Characterization Of Heusler Alloys

XeYZ type Heusler alloys a class of functional materials with excellent magnetic properties,and received widespread attention because of the different physical and chemical propertiesfrom other materials.So far,people mainly use the sputtering,molecular beam epitaxy,arc melting to prepare the different types of Heusler alloys materials.In this paper,Co₂MnSi thin films were prepared by a sputtering method which is controllable,high accuracy.Co₂FeAl nano-particles were prepared by a co-precipitation method which is low cost,flexible.In this work,firstly,the Heusler alloys CMS thin films were prepared by sputtering method.In this part,The effect of annealing temperature,Co atomic concentration on micro-structure and magnetic properties were studied.The Results show that:When the film was annealed at 350 ?,CMS thin film was in uncrystaline state.When the annealing temperature was increased over 400 ?,The CMS films have achieve a good?001?on the growth of epitaxial orientation,and have a good B2 structure.The long-range order parameters of the B2 structure were estimated to be almost 0.9 for annealing temperatures above 400 ?.The Ms increases to 1029 emu/cm3 and Hc decrease to 27 Oe,respectively,after annealing temperature at 650 ?,and the resistivity decreased.Then systematic CMS films have been prepared by changing the Co atomic concentration,the actual composition are basically consistent with expected.The CMS films have achieve a good?001?on the growth of epitaxial orientation,and has a good B2 structure.With the increasing of the Co atomic concentration,the intensity ratio of the?002?super-lattice peak to the?004?fundamental peak decreases form 0.53 to 0.31,and the degree of the B2 structure decrease.The value of Ms decreases from 864 to 812 emu/cm3,the Hc increases from 4 Oe to 70 Oe.The resistivity of CMS thin films decrease as the decrease of the measurement temperature.With the increasing Co concentration,the RRR value decrease form 1.73?Co50MnSi?to 1.39?Co70MnSi?,the half-metallicity of CMS films will be deteriorated.Secondly,the Heusler alloys Co₂FeAl nano-particles were prepared by a co-precipitation method.The effect of annealing conditions were studied firstly.The results indicate that Co₂FeAl nano-particles were in uncrystaline state with non-annealing.The purity of Co₂FeAl nano-particles increase as the improving annealing temperature,and achieve a good B2 structure.The Ms increases to 110 emu/g,the Hc decrease to 130 Oe,respectively,after annealing temperature at 800 ?.Then systematic Co₂?i+x?Fei-x;Al1-x?x=0.0,0.05,0.1,0.2,0.3,0.4?nano-particles have been prepared by changing the Co atomic concentration,The actual composition are basically consistent with expected.With the increasing Co concentration?x=0.0-0.3?,The Ms increases and the Hc decreases,respectively.Then,the Ms and Hc have a strong change when x=0.4 and 0.5.At last,the effect of the pH value on Co₂FeAl nano-particles shows that the Co₂FeAl nano-particles have a good B2 structure when the pH value form 5 to 7,and then disappear with the improving pH value.The Ms increases to 132 emu/g,and Hc decreases to 72 Oe,respectively,when the pH value at 7.