Control of multiferroic order by magnetic field in frustrated helimagnet MnI2. Theory

Abstract

We provide a theoretical description of frustrated multiferroic MnI2 with a spiral magnetic ordering in magnetic field h. We demonstrate that subtle interplay of exchange coupling, dipolar forces, hexagonal anisotropy, and the Zeeman energy account for the main experimental findings observed recently in this material (Kurumaji, et al., Phys. Rev. Lett. 106, 167206 (2011)). We describe qualitatively the non-trivial evolution of electric polarization P upon h rotation, changing P direction upon h increasing, and disappearance of ferroelectricity at h > hc, where hc is smaller than the saturation field.PACS numbers: 75.30.Kz, 75.10.Jm, 75.85.+t arXiv:1807.01693v2 [cond-mat.str-el]

Magnetic and electric properties of single crystal MnI2

“…According to the theoretical calculations, the spiral spin structure in MnI 2 contributes to the emergence of the FE polarization [27][28][29][30][31]. To investigate the magneto-electric coupling of MnI 2 , we fabricated a variety of capacitive Ag/MnI 2 /Ag devices with perpendicular top and bottom electrodes (the insert of figure 4(a)).…”

“…Considering the strong spin-orbit coupling for MnI 2 , the spiral magnetic order may break the inversion symmetry and consequently lead to the asymmetric charge distribution around the I-ions, resulting in the ferroelectric polarization. Based on this model, several theories were developed [28][29][30][31] and the previous experiments can be essentially understood. However, detailed experiments are still lacked to support the close relationship between the AFM and FE phases.…”

Mean-field approach for skyrmion lattice in hexagonal frustrated antiferromagnets

“…Magneto-dipolar interaction, despite being small, can play significant role in helimagnets properties including temperature-and magnetic-field-induced phase transitions (see, e.g., Refs. [22][23][24][25][26][27][28][29][30] ). Noteworthy, for magnetic ions in spherically-symmetrical L = 0 state (as, e.g., Gd 3+ in Gd 2 PdSi 3 31 ) the dipolar forces are of particular importance, since the strength of other anisotropic interactions is governed by the spin-orbit coupling 32 .…”

Phase competition in frustrated anisotropic antiferromagnet in strong magnetic field

“…Chiral magnetic structure appears due to frustration in many multiferroics 9 . The competition between different frustrating spin interactions often produces very complicated phase diagrams in the temperature-magnetic field plane which are interesting in themselves (as, e.g., in multiferroics MnWO 4 [10][11][12][13] and MnI 2 6,14,15 ). In the present paper, we study properties of frustrated anisotropic antiferromagnets (AFs) at small temperature in strong magnetic field close to the saturation one.…”