Multiferroic and magnetoelectric nanocomposites for data processing

Recent progress in preparing and understanding composite magnetoelectrics is highlighted. Apart from optimized standard solutions novel methods of switching magnetism with electric fields and vice versa with focus on magnetoelectric (ME) data processing in multiferroic and magnetoelectric nanocomposites deserve particular interest. First, we report on the patented MERAM, which uses the electric field control of exchange bias in a layered composite via an epitaxial magnetoelectric Cr 2 O 3 layer exchange coupled to a Pt/Co/Pt trilayer. It promises to crucially reduce Joule energy losses in RAM devices. Second, magnetic switching of the electric polarization by a transverse magnetic field in a composite of CoFe 2 O 4 nanopillars embedded in a vertically poled BaTiO 3 thick film produces a regular surface polarization pattern with rectangular local symmetry. Its possible use for data processing is discussed. Third, in the relaxor ferroelectric single-phase compound (BiFe 0.9 Co 0.1 O 3 ) 0.4 –(Bi 1/2 K 1/2 TiO 3 ) 0.6 polar nanoregions emerging from ferrimagnetic Bi(Fe,Co)O 3 regions embedded in a Bi 1/2 K 1/2 TiO 3 relaxor component transform into ferroelectric clusters and simultaneously enable congruent magnetic clusters. The local polarization and magnetization couple with record-high direct and converse magnetoelectric coupling coefficients, α ≈ 1.0 × 10 −5 s m −1 . These ‘multiferroic’ clusters are promising for applications in data storage or processing devices.