Comparison of first-principles methods to extract magnetic parameters in ultrathin films: Co/Pt(111)

Abstract

We compare three distinct computational approaches based on first-principles calculations within density functional theory to explore the magnetic exchange and the Dzyaloshinskii-Moriya interactions (DMI) of a Co monolayer on Pt(111), namely (i) the method of infinitesimal rotations of magnetic moments based on the Korringa-Kohn-Rostoker (KKR) Green function method, (ii) the generalized Bloch theorem applied to spiraling magnetic structures and (iii) supercell calculations with non-collinear magnetic moments, the latter two being based on the full-potential linearized augmented plane wave (FLAPW) method. In particular, we show that the magnetic interaction parameters entering micromagnetic models describing the long-wavelength deviations from the ferromagnetic state might be different from those calculated for fast rotating magnetic structures, as they are obtained by using (necessarily rather small) supercell or large spin-spiral wave-vectors. In the micromagnetic limit, which we motivate to use by an analysis of the Fourier components of the domain-wall profile, we obtain consistent results for the spin stiffness and DMI spiralization using methods (i) and (ii). The calculated spin stiffness and Curie temperature determined by subsequent Monte Carlo simulations are considerably higher than estimated from the bulk properties of Co, a consequence of a significantly increased nearest-neighbor exchange interaction in the Co-monolayer (+50%). The calculated results are carefully compared with the literature.arXiv:1904.06954v1 [cond-mat.mtrl-sci]

Complex magnetic textures in Ni/Irn/Pt(111) ultrathin films

“…The J ij for Co/Pt(111) from Ref. [63] (obtained using the Korringa-Kohn-Rostoker method), agree well to the present results. The small difference found in the case of J 1 was also reported in Ref.…”

Nature of Interfacial Dzyaloshinskii-Moriya Interactions in Graphene/Co/Pt(111) Multilayer Heterostructures

“…The D y values oscillate for n Co = 1 − 3 and converge to D y 0.3 meVµ −2 B afterwards. The fitted D y value for Co 1 Pt 5 is in agreement with the literature calculated with GBT and flat spin spirals [20,44], too, which are close to 0.5 meVµ −2 B . This methodology tends to yield larger energies than other electronic structure methods [44].…”

Isolated zero field sub-10 nm skyrmions in ultrathin Co films

“…7). The DMI in our calculations may also be overestimated due to the use of first-order perturbation theory, an effect which has been quantified to about 10–25% depending on the system 38,49 . To obtain a FM ground state in the simulations for hcp-Rh/Co/Ir(111), as in the experiment, we have reduced the calculated DMI by 50%, i.e., just below the critical value where a transition from a spin spiral ground state to a FM state occurs (see Supplementary Table 2 for values).…”

“…For Co, such exchange frustration has not yet been reported. However, the nearest-neighbor exchange interaction in Co monolayers can also strongly vary depending on the hybridization, for example it decreases by about 30% from Co/Pt(111) 38 to Co/Ir(111) 39 and by about 50% from Co/Pt(111) to Co/Ru(0001) 40 , which demonstrates the role of the interface for the strength of exchange interactions.…”