The functionality of any ferroic material depends on its domains. Consequently, their shape and manipulation in external fields are of major interest. In compounds uniting magnetic and electric order in the same phase, the magnetoelectric coupling on the level of the domains is, however, largely unexplored. For such so-called multiferroics it is therefore not known how exactly the electric or magnetic fields affect the multiferroic domains and their walls. In my talk I will discuss this issue. In particular, I will describe electric-field control of magnetic domains for compounds such as TbMnO3 and MnWO4 [1]. For compounds such as hexagonal YMnO3 and epitaxial SrMnO3 thin films [2], I will furthermore show that domain walls in multiferroics can be considered as new, mobile type of functional ferroic interface. Finally, I will present an example of all-optical control of a multiferroic state. The antiferromagnetic order parameter in multiferroic TbMnO3 is reversed repeatedly, using light pulses of two different colours. Switching depends on a unique relation between the wavelength of the light, its optical absorption and the electric polarization field induced by the antiferromagnetic order of TbMnO3 [3]. We access the multiferroic domains and their walls by nonlinear optics, here in the form of second harmonic generation — doubling of a laser frequency in a material.
References
[1] M. Matsubara et al., Science 348, 1112 (2015)
[2] C. Becher et al., Nature Nano. 10, 661 (2015)
[3] S. Manz et al., Nature Phot. 10, 653 (2016)