First-principles Study Of Cr-doping NiAs-type And Zinc-blend-type MnTe

Both MnTe and CrTe are transitional metal magnetic material, with similar crystallattice structures, together with their curie temperatures close to room temperature.Therefore, Mn1-xCrxTe compounds display high practical value. Based on the giantmagnetoresistance and the tunneling magnetoresistance effect in spinelectronics, Mn1-xCrxTe magnetic metal films have been made in the experiments, and areapplied to quantum devices, such as a spin valve and magnetic head. Besides, they can beused into magnetic storage devices and photoelectric devices, which have the adventagesof non-volatile, higher speed, lower power consumption, higher degree inintegration, bright color and so on.MaterailsStudio6.0program in CASTEP software package, based on the densityfunctional theory, is employed to calculate Mn1-xCrxTe compounds. In NiAs-type ones, theenergy band structure and density of states of ferromagnetic and antiferromagneticMn1-xCrxTe with x=0,0.1,0.2, and0.3have been computed, besidesthe geometry optimization of the supercell by1×1×5. Moreover, the calculations weredone on energy band and density of states of ferromagnatic and antiferromagneticMn-difficiency Mn1-x□xTe cell with x=0.1. In the Zinc-Blend type, calculations weredone on ferromagnatic and antiferromagnetic energy band and density of states, based onthe supercell of MnTe1×1×2, with x=0.125,0.25. The Mn-difficiency Mn1-x□xTe hasalso been computed.Through analyzing the data and images, the conclusions have been drawn, as follows:in the Cr-doped NiAs-type one, d electrons of Cr atomic and p electrons of Mn atomichave hybrid, the subtraction of the area which spin down and up in valence band becomesnegative, resulting in change of magnetic properties. MnTe is an antiferromagnetichalf-metal. When x=0.2, ferromagnetic energy is low, and the up-spin has no conductionband, Mn0.8Cr0.2Te exhibits semiconductor. When x=0.3, ferromagnetic becomes morestable, spin band continue to move to opposite directions, Mn0.7Cr0.3Te becomes half-metalagain. The absence of Mn0.9□0.1Te, is an semiconductors with indirect and narrow bandgap. In the whole system, d electronic is localized, which make Mn1-xCrxTe compounds may be half-metal, semiconductor, which depends on the x value.The hybrid method in Mn1-xCrxTe of ZB type is also p-d one. When x=0.125,Mn0.875Cr0.125Te is antiferromagnetic half-metal; while x=0.25, Mn0.75Cr0.25Te is aferromagnetic half-metal. The absence of Mn0.875□0.125Te is semiconductor, which arisesfrom Mn atom-vacancy as a result of the large conduction band. In addition, the values ofdensity of states in the Fermi surface are close to0, similar to semiconductor, illustratesthat this system is stable.