Magnetic And Perpendicular Magnetic Anisotropy Of Mn_xGa|Co₂FeAl Superlattices By First-principles Calculations

With the development of society,people's storage requirements for heavy information are getting higher and higher.The magnetic random access memory?MRAM?has attracted extensive attention due to its non-volatile,high speed,high density,low power consumption,and is considered to be an ideal memory in electronic devices.The main challenge for implementing STT-MRAM in high-density and high-speed memory is seeking for an advantageous magnetic material as building block layers.Ideally,it should combine the thermal stability?large magnetic anisotropy constant,Ku?,low critical current to switch magnetization?low magnetic damping constant,a?,flexible saturation magnetization?small magnetic moment,Ms?,large tunnel magnetoresistance ratios?TMR??high spin polarization,P?.Finding materials that possess high perpendicular magnetic anisotropy?PMA?and low magnetization is a key challenge for the potential application to the magnetic tunnel junction?MTJ?.Through systematic density functional theory?DFT?calculations,we have studied a series of Mn_xGa|Co₂FeAl?x=1,1.66,3?superlattice?SL?models by individually changing the thickness of Mn_xGa hard-magnetic layers and Co₂FeAl soft-magnetic layers as well as controlling the interface magnetic couplings.Our results demonstrated that total magnetic moments of the SLs can be well balanced to a small?zero?value as the antiferromagnetically coupled Mn_xGa and Co₂FeAl layers have the matching thickness and appropriate interface.Strong PMAs of Mn_xGa bulks can be well preserved in SLs,being up to 0.38,0.37,0.22 meV/Mn for x=1,1.66,3,respectively,which are weakly dependent on the layered thickness?flexible lattice constants of SLs?but strongly on the magnetic coupling with Co₂FeAl layers.The ferromagnetic/antiferromagnetic coupling at Mn-Co interface often generates small/large negative interface PMA and thus it would diminish the PMA of SLs;however,Ga-Co interface was found to give large/small positive contribution to the PMA of SLs.Typically,Ga-Co?MnGa-Co?interface is proposed to be the most favorable one for experimentally heteroepitaxial growth of Mn_xGa|Co₂FeAl SLs,because it can guarantee these SLs to present high stability,large PMAs,and tunable magnetic moments.In summary,we have investigated the geometric,electronic and magnetic properties of Mn_x Ga|Co₂FeAl?x=1,1.66,3?SLs by using the first-principles calculations.The magnetic properties as functions of chemical composition,various interface and layer thickness have been comprehensively examined.In addition,the interpretation of the PMAs is supported by the results of PDOS analysis of the magnetic atoms on the representative layers via the framework of second-order perturbation.Based on these considerations,theoretically investigating Mn_xGa|Co₂FeAl SLs and providing a physical picture are desired not only for scientific study but also for potential MTJ device applications.