Local environment effects in the magnetic properties and electronic structure of disordered FePt

Local aspects of magnetism of disordered FePt are investigated by ab initio fully relativistic full-potential calculations, employing the supercell approach and the coherent potential approximation (CPA). The focus is on trends of the spin and orbital magnetic moments with chemical composition and with bond lengths around the Fe and Pt atoms. A small but distinct difference between average magnetic moments obtained when using the supercells and when relying on the CPA is identified and linked to the neglect of the Madelung potential in the CPA.

Figure 1

Structure diagrams of the SQSs used in this study.

Figure 2

Spin-polarized density of states for Fe and Pt sites. Data for ordered $L{1}_0$ structure are compared to data obtained by averaging over all sites in the SQS-4, SQS-8, and SQS-16 supercells, to data obtained by averaging over all sites in the SQS-4, SQS-8, SQS-16, and SQS-32 supercells, and to the CPA result. The calculations were performed using the sprkkr code.

Figure 3

Spin and orbital magnetic moments for Fe sites in various SQSs shown as a function of the number of Fe atoms in the first coordination sphere. The CPA results are shown for comparison. The data were obtained using the sprkkr code.

Figure 4

As in Fig. 3, but for Pt sites.

Figure 5

Electronic charge for Fe sites in various SQSs shown as a function of the number of Fe atoms in the first coordination spheres. The CPA result is shown for comparison. The data were obtained using the sprkkr code.

Figure 6

Spin magnetic moment for Fe sites in various SQSs shown as a function of the charge. The CPA result is shown for comparison. The data were obtained using the sprkkr code.

Figure 7

Electronic charge at the Fe sites (top panel) and at the Pt sites (bottom panel) as a function of $N_{\text{Fe}}$ for SQS-4, SQS-8, SQS-16, and SQS-32 obtained with the Madelung potential either included or ignored. The CPA result is shown as well. The calculations were done using the sprkkr code.

Figure 8

As in Fig. 7, but for spin magnetic moments.

Figure 9

Optimized interatomic distances for the first coordination shell in SQS-4, SQS-8, SQS-16, and SQS-32. Average values are shown by horizontal lines. Results were obtained using the wien2k code, with the exchange-correlation potential parametrized within the LDA (left panel) and within the GGA (right panel).

Figure 10

Change of the spin magnetic moment $\mathrm{\Delta }{\mu }_{\mathrm{spin}}$ for a Fe atom (top panel) and for a Pt atom (bottom panel) plotted as a function of change of the average bond length $\mathrm{\Delta }{\overline{d}}_{\text{Fe-Fe}}$ or $\mathrm{\Delta }{\overline{d}}_{\text{Pt-Fe}}$. The calculations were done using the wien2k code.