Nanocrystallization Preparation And Physical Properties Of CrAl Alloys

Spintronic materials are a new kind of functional material which can utilize both the spin and charge properties of electrons,this characteristic is expected to produce more excellent devices in the future.Cr₃Al is a half-metal material with the DO₃structure which have high spin polarization,and haven't been prepared in previous research.In this paper,the Cr-Al series films and nanowires have been prepared by magnetron sputtering to explore the preparation technology of Cr₃Al films and nanowires with the DO₃structure and series of representations have been taken for the samples.The electronic structure and magnetic moment were calculated by theoretical calculation,and the results are compared to the one from experiments.The Cr-Al series films prepared on the glass substrate is the cubic structure when the substrate temperature is 100?.The Cr content has great effect on the equilibrium lattice constant,magnetic moment and so on.With the increase of Cr content,the equilibrium lattice constant decrease,and the experiment results are less than the theoretical values.The measurement results at low magnetic field demonstrate that Cr-Al series films all have very small coercive force,which is one of the properties of the soft magnetic material.Comparing the electronic structure and results from magnetic measurements with the theoretical results,the crystal structures of Cr-Al films have no voids but the Al atoms replace the Cr at C site.In addition,the spin polarization increasing monotonously with the Cr content.The variations of results from magnetic measurement and theoretical calculation are basically consistent.Cr₃Al films have been successfully prepared on the glass substrate with different substrate temperature.The measurement results indicates that the substrate temperature have great influence on the atomic order,density and equilibrium lattice constant and so on.With the increase of substrate temperature,the lattice constant of samples increases continuously.Since the expanding of crystal lattice will lead to the decrease of the density and atomic order,the magnetic moment decrease.Thus,the experimental lattice constants are all less than theoretical values.The electronic structure and magnetic results from theoretical calculation based on the experimental lattice constant 5.83?indicates that Cr₃Al possess zero-gap half-metal properties under this lattice.The magnetic moment results from experiment and theoretical calculation reach an agreement.The R-T curves imply that the sample has the half-metal-like electronic transport property and positive magnetoresistance higher than 2%in the temperature range of 2?250 K.Nanostructure with different configurations can be made by using the AAO template due to the aperture and technological parameters for preparing have a great impact on the structure of the samples.According to the preparation technology for Cr₃Al,technological parameters have been searched for the growth of Cr₃Al film on the AAO template by employing the magnetron sputtering.Cr_0.76Al_0.24nanowires were successfully prepared through the adjustment of aperture and technological parameters.The orientation of growth of Cr_0.76Al_0.24measured by high resolution is agreed with the results from XRD.In term of the results from magnetic measurement,the sample has stronger magnetism with the increase of the temperature of substrate.Cr_0.76Al_0.24nanowires possess properties of soft magnetic material on the basis of the results under small magnetic field.