Magnetic Moment And Magnetic Anisotropy Of Tm|FePt|MgO Heterostructures By First-Principles Calculations

With the rapid development of information technology,especially the rise of concepts such as large data and cloud storage,the industry's demand for massive information storage is getting higher and higher.At present,the hard disk is the main storage device in all kinds of magnetic storage media due to its high density,easy portability and low price.Increasing the storage density has been a tireless pursuit of scientific researchers.However,one of the key factors that restrict the increase of storage density is the magnetic anisotropy energy?MAE?,which is the determinants of preventing thermal disturbance,overcoming superparamagnetic effect and ensuring the stability of information storage.Therefore,searching for magnetic recording materials with high magnetic anisotropy is the key point to improve the storage density.In a large number of storage media,the face-centered tetragonal?fct?L1₀ phase of the 3d-5d binary based alloys such as FePt have recently been the subject of much attention because of their strong perpendicular magnetocrystalline anisotropy?PMA?about 7×10⁷ergs/cm³ and potential applications for the fabrication of ultrahigh density data-recording media.It has been shown that PMAs can be promoted through the feasible modifications such as the substitution of excellent ferromagnetic layers as well as the overlayer coating on them.Here,we perform the first principles calculations of magnetic moments and PMAs in the TM|L1₀-FePt|MgO sandwich systems to elucidate how the presence of various transition metal?TM?overlayers would impact on their structural and magnetic properties.?1?Throughout our study we make comparisions between the Fe-termination and Pt-termination of the FePt|MgO system,exploring the structure,adsorption energy and the magnetic moment of interfacial atoms in details.We observe that the Fe-termination and the Pt-termination give 2.32?and 2.64?,respectively,owning to the stronger Fe-O bonding over the Pt-O bonding,which suggests that the Fe-terminated interface to MgO is more energetically stable than the Pt-terminated one.?2?we systematically report the magnetic results of the TM|FePt|MgO heterostructures with Fe-termination by using a wide range of transition metal elements?3d-TM:Fe,Ni,Cu;4d-TM:Rh,Pd,Ag;5d-TM:Ir,Pt,Au?as the overlayers that are individually contacted with the FePt slab.Moreover,we demonstrate that in comparison with the results of FePt bulk and FePt|MgO heterostructure,the changes in magnetic moments of TM|FePt|MgO are faint and negligible,but the changes in the PMAs are always giant and positive,e.g.,the PMA of Fe|FePt|MgO,the largest one among all our studied systems,is about 2 times larger than that of FePt|MgO.?3?In order to quantitatively elucidate the origination of the PMA in TM|FePt|MgO heterostructure,on the basis of the layer-resolved analyses,the interfacial PMAs at the TM|FePt and FePt|MgO interfaces are extracted to be 3.31?9.40 meV and 3.32 meV,respectively,which are at least 3 times larger than 0.93 meV/ML of the interior FePt layers.In addition,we have taken FePt|MgO,Fe|FePt|MgO and Pt|FePt|MgO as the typical systems and explored the in-plane strain effect on the PMA by varying the in-plane lattice constants a of these heterostructures.It has been found that the MAE increases first and then decreases with the increase of in-plane lattice constant,and the magnetization changes from perpendicular to in-plane when the stretching strain is large enough for TM|FePt|MgO heterostructures.Thus,we illustratively verify that the magnitudes of the PMAs of TM|FePt|MgO can be turned in a large range by varying the TM layer and the in-plane strain.?4?In order to explore the origin of PMA,the underlying mechanism responsible for the interfacial enhancements as well as the strain inducing variations of the PMAs is unveiled by our layer-and orbital-resolved electronic structure analyses under the second-order perturbation method.We have revealed that the PMAs of TM|FePt|MgO heterostructures are dominantly contributed by the Fe-3d orbitals through the SOC interactions between the occupiedd_x2-y2and the unoccupiedd_xystates.In summary,we have carried out the first principle calculations on FePt|MgO and TM|FePt|MgO heterostructures for their geometric structures,magnetic moments,magnetic anisotropy and electronic structures.Analysing the different results,we demonstrate the intrinsic physical mechanism of the PMAs of TM|FePt|MgO heterostructures including the contributions from TM|FePt interface,FePt interior layers and FePt|MgO interface,suggesting the possibilities of the realisations of TM|FePt|MgO heterostructures as the novel spintronic devices and the next generation of ultrahigh-density storage devices.