Structural, electronic and magnetic properties of the ordered binary FePt, MnPt, and CrPt3 alloys

Abstract

We perform ab initio simulations to investigate the structural, electronic and magnetic properties of the ordered binary FePt, MnPt, and CrPt3 alloys. In particular, equilibrium structural lattice parameters, electronic properties such as density of states (DOS), partial density of states (PDOS) and electronic band structure of each binary alloys are investigated and interpreted. Moreover, the magneto-crystalline anisotropy energies (MAE) are calculated. We found MAE values of FePt, MnPt and CrPt 3 ordered alloys to be 2.66, 0.46 and 0.42 meV/f.u., respectively, corresponding to magneto-crystalline anisotropy constant K of 7.6 Â 10 7 , 1.3 Â 10 7 and 1.1 Â 10 7 erg/cm 3 , respectively. The large MAE and K values reveal that FePt, MnPt and CrPt 3 binary alloys are eligible to be key components in magneto-optical and opto-electronic devices. In addition, we estimated the Curie temperatures of the three ordered alloys from exchange energy. We found the T C of L1 0 -FePt, L1 0 -MnPt and L1 2 CrPt 3 to be 955 K, 989 K and 762 K, respectively. The high Curie temperatures obtained enable the ordered alloys to serve as write assist in Heat-Assisted Magnetic Recording (HAMR). We believe that our findings would pave the way to fabricate bulk and thin films based on the ordered binary FePt, MnPt, and CrPt 3 ordered alloys that have attractive electronic and magnetic properties.

Phonon, Electron, and Magnon Excitations in Antiferromagnetic L1$_{0}$-type MnPt

“…While bands are crossing at the Fermi level, the density of states itself is very low and exhibits a significant dip within about 0.5 eV. This is similar to what was reported by Umetsu et al from LMTO-LSDA-ASA simulations, 10 and also agrees with DFT-LSDA simulations by Lu et al 30 as well as DFT-PBE by Wang et al 28 and Alsaad et al 29 We compute the electronic specific heat using the thermodynamic average of the internal energy U at temperature T and the Sommerfeld expansion, leading to…”

“…In both expressions m stands for the sub-lattice magnetization and N is the total number of magnon energies sampled by the q point grid. Here we use a 30×30×30 q-point grid to evaluate these expressions and obtain T MFA N =1250 K and T RPA N =1190 K. Both values are slightly larger than measured values of 975 K 7 and 970 K, 10 or another DFT result, using exchange coefficients, of 989 K. 29 A similar overestimation of the experimental result on the order of 25 % by this approach is also reported e.g. for ferromagnetic bcc Fe and antiferromagnetic NiO.…”

“…where m i is the magnetic moment at site i consistent with our DFT simulations and γ L = γ/(1 + α 2 ) is the renormalized gyromagnetic ratio. γ is a gyromagnetic ratio and we use the default value of an isotropic Gilbert damping constant α=0.1 implemented in UppASD, 27 which 28 3.98 3.98 3.72 3.7 -DFT-PBE 29 4.03 4.03 3.69 4.3 0.0 DFT-LDSA 30 3.99 3.99 3.70 3.8 0.0 LMTO-LDSA 10 ---3.6 0.0 Exp. 7 4.00 4.00 3.67 4.3 -Exp.…”

Dzyaloshinskii-Moriya interaction induced by an ultrashort electromagnetic pulse: Application to coherent (anti)ferromagnetic skyrmion nucleation

“…We consider model systems in the form of 3d transition metal unsupported monolayers (UMLs), in which the d -band is progressively filled from Mn to Fe, Co, and Ni, as well as unsupported trilayers of Fe/Pt/Fe, Pt/Fe/Pt, and Pt/Mn/Pt. We use the lattice parameters and crystal structures of bulk Mn, Fe, Co, Ni, and L 10 PtFe or PtMn binary alloys [37]. A static electric field is applied perpendicular to the film plane, which allows us to circumvent the calculation of the long-range Coulomb-type interaction present in bulk systems.…”

Making a case for femto- phono- magnetism with FePt

“…Computational parameters: All calculations are performed for L1 0 structure of FePt [32] with lattice parameter a=3.88angstom and c=3.73 angstrom. A k-point set of 12×12×8 was used for real-time TDDFT calculations.…”