Nature of the spiral state, electric polarisation and magnetic transitions in Sr-doped YBaCuFeO${}_5$: A first-principles study

Abstract

Contradictory results on the ferroelectric response of type II multiferroic YBaCuFeO${}_5$, in its incommensurate phase, has of late, opened up a lively debate. There are ambiguous reports on the nature of the spiral magnetic state. Using first-principles DFT calculations for the parent compound within LSDA+U+SO approximation, the multiferroic response and the nature of spiral state is revealed. The helical spiral is found to be more stable below the transition temperature as spins prefer to lie in ab plane. The Dzyaloshinskii-Moriya (DM) interaction and the spin current mechanism were earlier invoked to account for the electric polarisation in this system. However, the DM interaction is found to be absent, spin current mechanism is not valid in the helical spiral state and there is no electric polarisation thereof. These results are in good agreement with the recent single-crystal data. We also investigate the magnetic transitions in YBa${}_{1-x}$Sr${}_x$CuFeO${}_5$ for the entire range $0\le x\le 1$ of doping. The exchange interactions are estimated as a function of doping and a quantum Monte Carlo (QMC) calculation on an effective spin Hamiltonian shows that the paramagnetic to commensurate phase transition temperature increases with doping till $x=0.5$ and decreases beyond. Our observations are consistent with experimental findings.

8 pages, 7 figures

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Cited by in corpus (7)

• Design of magnetic spirals in layered perovskites: extending the stability range far beyond room temperature
• Tuning the tilting of the spiral plane by Mn doping in YBaCuFeO5 multiferroic
• Effect of (Cu/Fe)O5 bipyramid size and separation on magnetic and dielectric properties of rare earth layered perovskite LaBaCuFeO5 and LuBaCuFeO5
• Signature of half-metallicity in ${\text{BiFeO}}_{\text{3}}$
• Low temperature magnetic and dielectric properties of LnBaCuFeO5 (Ln = Nd, Eu, Gd, Ho and Yb)
• Skyrmions at Vanishingly Small Dzyaloshinskii-Moriya Interaction or Zero Magnetic Field
• Orbitally driven spin reorientation in Mn doped YBaCuFeO${}_5$