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An ambitious objective of the modern magnetism is the control of the magnetization of materials via the application of an electric field [1]. This objective is obviously driven by the important fallout on the electronic industry that this possibility would open. The magnetization control with electric field is now possible in those materials that display a spontaneous coupling between ferroelectric (FE) and ferromagnetic (FM) orders that are called multiferroics. Unfortunately the low magnetoelectric coupling coefficient like in BiFeO3 [1] and sometime the low Tc have for the moment limited the use of these materials in real devices. Two main routes are currently explored to overcome this limitations: the doping of mutiferroics with substitutional magnetic impurities and the realization of heterostructures in which different properties like ferroelectricity and ferromagnetism are artificially coupled to obtain high magnetoelectric coupling coefficient. The advantages and drawbacks of these two different solution will be presented together with two model examples: the Bi2FeCrO6 double peroskite [3] and the Fe/BaTiO3 interface [4]. In the first example we present the magnetic properties of Bi2FeCrO6: a double peroskite obtained by replacing half of the (111) crystal planes of Fe, in the BiFeO3 structure, with Cr planes. This new structure is predicted to display an artificial ferrimagnetic structure in spite of the normal antiferromagnetic configuration that will lead to an increase of the magnetoelectric coupling [5]. In the second case we present the chemical and magnetic analysis of the Fe/BaTiO3 interface, probably the most representative FE/FM interface, in which we have observed the formation of iron oxide at the interface that surprisingly shows a magnetic phase transition driven by the FE state of the BaTiO3.
[1] F. Matsukura et al. Nature Nanotech. 10, 209 (2015)
[2] C. Ederer and C. J. Fennie, J. Phys. Condens. Matter 20, 434219 (2008)
[3] G. Vinai et al. APL Mater. 3, 116107 (2015)
[4] G. Radaelli et al. Nat. Commun. 5, 3404 (2014)
[5] P. Baettig et al., Phys. Rev. B 72, 214105 (2005)
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