Abstract:
In general, the magnetization of a solid is governed by the spins of the electrons,
while the charges of electrons or ions are responsible for electric polarization and thus
they can be controlled by applying external magnetic and electric fields, respectively.
Magnetoelectrics are one of the interesting classes of materials, where magnetization can
be induced by applying electric field and electric polarization can be induced by applying
magnetic field [1,2]. Therefore, these materials offer a great platform for electric field
controlled magnetism and vice versa. The work on magnetoelectric effect started more
than a century ago and it has progressed through the pioneering works of many great
scientists (Figure 1.1) [1,3,4]. In 1894, Pierre Curie first proposed magnetoelectric effect
on the basis of symmetry [5]. Later, Piccardo, Debye and Van Vleck suggested that
magnetoelectric effect is impossible [6,7]. After two decades, Landau and Lifshitz
showed that magnetoelectric effect may appear in the materials with certain types of
magnetic and crystal symmetry [8]. Dzyaloshinskii in 1959 predicted that the
antiferromagnetic structure of Cr2O3 should allow linear magnetoelectric effect [9]. This
prediction was confirmed by experiments by two different groups. Astrov discovered
electric field induced magnetization below magnetic ordering temperature in Cr2O3
[10,11]. Rado and Folen demonstrated the reverse effect i.e., the magnetic field induced
electric polarization in Cr2O3 [12]. However, the magnetoelectric coefficient of Cr2O3 is
small for application. Thus, many theoretical and experimental investigations were started
in search for room temperature magnetoelectric materials with higher magnetoelectric
coupling.
