Electric-field-induced spin disorder-to-order transition near a multiferroic triple phase point

Abstract

The emergence of a triple phase point in a two-dimensional parameter space (such as pressure and temperature) can offer unforeseen opportunities for the coupling of two seemingly independent order parameters. On the basis of this, we demonstrate the electric control of magnetic order by manipulating chemical pressure: lanthanum substitution in the antiferromagnetic ferroelectric BiFeO3. Our demonstration relies on the finding that a multiferroic triple phase point of a single spin-disordered phase and two spin-ordered phases emerges near room temperature in Bi0.9La0.1FeO3 ferroelectric thin films. By using spatially resolved X-ray absorption spectroscopy, we provide direct evidence that the electric poling of a particular region of the compound near the triple phase point results in an antiferromagnetic phase while adjacent unpoled regions remain magnetically disordered, opening a promising avenue for magnetoelectric applications at room temperature. The triple point is a well-known feature on pressure–temperature phase diagrams. A multiferroic triple point is now reported for La-doped BiFeO3; La concentration and temperature are the phase variables and the phases display different spin (dis)order.